At the end of the episode, Mugen is seen with a new sword on his back. That sword is from medieval times and did not exist in the Edo period of Japan.
Umanosuke's chain scythe
This nasty item is essentially the on-steroids version of a standard ninja weapon, the Kusari-gama in this case, a Kusari-gama with the chain attached to the blade instead of the hilt, and seemingly spring loaded (if not downright rocket-launched) so that the blade can both be fired and retracted with great force. I think it is perfectly reasonable to say that no such thing existed in Edo Japan.
Denkibou's metal claws
Essentially it's another ninja weapon (Iga ninja, to be exact) called a tekko-kagi. Worn on the back of the hand, just as this set is. However, I do not know that tekko-kagi were ever made with folding claws like these; the only examples I can find images of look to have been cast in a single piece. So I'll tentatively say these are probably anachronistic; they're based on something of the time, but their technology may be too extreme for the Edo Period.
Heavy - artillery wheelchair
The earliest known image of a wheelchair appears on a Chinese sarcophagus from the 6th Century (what didn't the Chinese have first?), and in the 16th Century King Philip of Spain used an elaborate custom rolling chair. Moreover, this one is plainly made of wood. The design is probably too advanced for the time --this looks like the ones built in the U.K. in the 18th century-- but if it were just a wheelchair, it wouldn't be impossible. I can even excuse the amount of storage space under the seat and in the hollow arm, since those could, after all, be used for innocent purposes. However: the gun mounted in the armrest definitely takes it out of the "nothing unusual for the time" category. Again, like his brothers' weaponry, Toube's chair is a plausible device amped into implausibility.
The store where Jin and Mugen buy the castilla is exactly the same one, Fukusaya, that's famous for its castilla in Nagasaki today? They claim to be the only place making it from the original unaltered Portuguese recipe, as they have ever since those days. Here are the real store and the frame
Mugen told Jin and Fuu that he killed a man that helf the sign of the shogunate: that man was Mito Komon, the star of the longest-running TV show in Japanese history, which began in 1969 and is still running in 2005, after more than 1000 episodes. Though a fictional character, Komon is based on a real person, Tokugawa Ieyasu's grandson Tokugawa Mitsukuni (1628-1700). The real Mitsukuni was the lord of Mito Province (now Ibaraki prefecture), a reclusive scholar best known for the amount of research he contributed to a very important and influential history, the Dai-Nihon-Shi ("Great History of Japan"). He was called by his literary pen-name, Komon ("yellow gate"), hence "Mito Komon". His fictional counterpart travels the country in the guise of a retired merchant, giving him regular reasons to right wrongs and aid the oppressed. The signature moment of every episode, apparently, comes near the end, when in the middle of a violent struggle with the villain of the week, Komon's attendants interrupt to flash in the evil-doer's face their master's inro, a lacquered case bearing the Tokugawa crest (just as happens in the story Mugen recounts), and proclaim that the man he's fighting is none other than the current Shogun's uncle, Lord Mitsukuni of Mito. ("Hikae! Kono mondokoro ga me ni hairan ka?" "Down! Can you not see this emblem?").
During the baseball match, the Japanese teams catcher was a dummy, with hiragana characters drawn for its face.
The use of dowsing to find something underground is not at all anachronistic; it's what Shige uses that puts this one on the list. Zantetsuken reports: "The use of dowsing tools goes back in China to at least 2500 years ago, 4000+ in Egypt. No idea if they were used in ancient Japan, but being in China that early I'd think it likely. Traditionally, pendulums and forked rods ("Y-rods") appear to be the oldest forms: note the Chinese rods were of the forked variety.
Shige's line to our trio about the whereabouts of the treasure ("Aru to shika ienai. Dakara koso nai to ii kire nai" that was translated as "I can tell you only that it exists exactly. Therefore I can't tell you that it doesn't") is a direct quote from Shigesato Itoi in reference to the Tokugawa treasure, and the name "Shige" could very well be a reference to him also. As Itoi is well known to be a huge fan of the Beatles and 1960s rock music, he may even have some bearing on the appearance of Shige, who many have noted has a "rock star" presence and attitude, and whose haircut and biwa lute give him a particular resemblance to the late Rolling Stones' founder Brian Jones
Although the venom of the deadly Japanese fugu ("pufferfish") is frequently quoted as an ingredient in zombie-making potions (and there are cases of people eating improperly prepared fugu who fell into a deathlike sleep for several days and then returned to life) there is absolutely no tradition of zombies in Japanese folklore. None: neither the traditional Haitian "walking-dead slave" nor the film-style "cannibal corpse". Shige's flesh-eating revenant laborers are a wild combination of 20th Century American film zombies of the "Night of the Living Dead" school, genuine traditions about the restless spirits of the Heike/Taira warriors, and the modern-day use of zombies in Japanese plays and fiction as a metaphor for the cost of forgetting the lessons of the past and of past wars, especially World War II.
The idea of a gun that would keep up a continuous stream of fire attracted inventors early in the development of firearms. In 1718 James Puckle invented what he called his Defence Gun. Placed on a tripod it was a large revolver with a cylinder behind its single barrel; the cylinder had to be turned manually. Using a standard flintlock weapon, a soldier could be expected to fire three times per minute, but the Puckle gun could fire up to nine shots per minute. In 1861 Richard Jordan Gatling, a trained dentist from North Carolina, produced an effective mechanical gun. The Gatling Gun consisted of six barrels mounted in a revolving frame.
Canopy beds go back to at least the 1500s, and probably before. Only the wealthy tended to have them, of course, but many European monarchs had very elaborate ones, sometimes involving mirrored "ceilings" Also, they tended to be huge--how does a bed up to four meters wide sound? But Xavier's is very modern looking...
So, in Edo Japan: stuffed animals, homemade, probably. Teddy Bears, no. Modern-looking Teddy Bears (as opposed to 1903 ones) were not made back then.
The word graffiti derives from the Greek word graphein meaning: to write. This evolved into the Latin word graffito. Graffiti is the plural form of graffito. Simply put, graffiti is a drawing, scribbling or writing on a flat surface. Today, we equate graffiti with the "New York" or "Hip Hop" style which emerged from New York City in the 1970's.
The kids who try to rough up Jin at the dojo have a butterfly knife or balisong. Though one school of thought claims these date back to Malaya or Polynesia circa 800, the authoritative view seems to be that they originated in 1700s France and were taken to the Philippines by Spanish sailors, whence they made their way through Asia.
Mugen claims to have invented this design, it's pretty simple; he might have dreamed it up with a flick of the brush. However, he wasn't the first (though he's close!). John Wallis (1616-1703), considered one of the most original English mathematicians of his day, was the first to use it in print with the meaning of "infinity", in his 1655 publication Arithmetica Infinitorum. He in turn had derived it from a Roman symbol meaning "one thousand". So the symbol does pre-exist Mugen's use of it as a personal tag, but considering that he'd have no way of knowing that his tag had already been used with the same meaning in another country about 20 years earlier--or by the Romans, for that matter
Note that though the Niwa twins' tagging crew uses mainly brushes for its work (and the paintbrush is an ancient tool, perfected in medieval China, but dating back at least 20,000 years), they also employ a spray pump. Not invented yet by a long shot.
During the Edo period the Matsumae family (Matsumae - Han) controlled the northern domanin of Hokkaido. The Matsumae used force to clear the way for Japanese emigration into Ainu territory. Referring to the episode, Okuru's clothing, the building in his village and the description he makes of the land he comes from strongly suggest that he is from Ainu.
Training methods at the Mujuu
We see Jin and Yukimaru sparring with shinai (training swords made of bamboo). Unlikely for this time period. Yoshinori Kono writes that modern kendo using shinai and bogu (protective equipment) is generally believed to have originated during the Kyoho period [1716-1735]. Some suggest that the modern kendo shinai was developed by Tanetake Nakanishi, second headmaster of the Nakanishi-ha Itto-ryu (c. 1750-60?). Tanetake adopted the practice of uchiaigeiko--training through competitive matches between opponents equipped with shinai and bogu-- because he felt that kata training alone was a too difficult and time-consuming way to learn. (Robert Mele, who brought this anachronism to my attention, also offered the 1750 date and Nakanishi Chuzo as the inventor's name).
The power source of the brothel
First of all, the elevator. While primitive animal- or man-powered lifts and hoists had been in use for ages--there was even one in the Roman Coliseum-- this looks and operates like an Otis-style hydraulic or at least counterweighted elevator, of which there's no known example earlier than 1743 (Louis XV commissioned it for his personal chambers in the Palace of Versailles). The hydraulic elevator is generally said to have been invented in the 1800s and was firmly established by Elisha Otis' invention in 1853 of the safety brake. Using the Versailles example, the brothel's lift is just marginally possible, but very iffy, considering Japan's total isolation from the West at this time.