We know about Japanese armourers modifying and imitating European pieces, but did the reverse also happen?
http://www.flickr.com/photos/thoog/1548478937...2352388212
I've noticed this helmet bears a striking resemblance to a kabuto. Not just with the ribbed bowl, visor and neck guard, but also with the crest holder and the portion on top in place of the tehen. You'll even notice the ribbed portion of the bowl transitions to a smooth portion, looking very much like the koshimaki on Japanese helmets.
There just seem to be to many similarities to be coincidence.

Coincidence. The lobster tailed helmet used in europe during the 17th century was a adoption of (some) middle eastern style armor. The helmet would have been concurrent with morions, cabbasets, and burgonets for the same reasons these helmet styles emerged; good visibility with decent protection. It filtered into eastern europe from the warfare against the middle east, and it then filtered into western Europe as a result of interaction (part of it being militarily) between the two areas.

Rather than copied from kabuto, it's copied (via Turkish/Tatar helmets) from a common Central Asian style which also influenced Chinese and Korean helmets.

Here is one example: http://www.metmuseum.org/toah/works-of-art/2005.146

This would have had a lamellar neckguard, or possibly brigandine neckguard, and possibly brigandine cheekpieces (perhaps with protection for the lower face), rather than the large lames on the European/Turkish versions (which often had a one-piece neckguard with fake lames embossed on it).

I've not looked closely at the evolution of Japanese helmets, so can't say which of the features in common you see in kabuto might have come from Chinese/Mongol/Korean helmets.

Pretty much all armour the Japanese ever adopted was copied from someone else. There is no reason to think that Europeans needed to copy anything from Japan because they would have already seen it elsewhere.

Europe didn't really get into a whole lot of contact with Japan until the end of the 16th century when armor was being used less and less. It was the French 17th century court that introduced the popular copying of Chinese and Japanese items. I have seen a French made 18th century copy of a katana that looked a bit odd. But I have not seen any European copies of Japanese armour from that time even though there were Japanese suits that were brought back as presents or some such. A while ago I also saw a 18th century painting that included a suit of Japanese armor I think the reason for not copying Japanese armor may have been that European armor was just more developed due to the availability of iron ore and the introduction and use of firearms against it... The Japanese had to develop Namban Do and what they called "bullet proof armour" to copy the European designs against the use of the introduced firearms the Prortugese brought to Japan.

Its all really mixed together... The Mongols and Turkik tribes running into each other in the steppes... You see the same helmet shapes and ideas all over the place that got tuched by them. Polish (Golden Horde), Hungarian (Madjar), Russians, Turks. The entire Turkmen tuched areas include North Africa, Turkey, Middle East, Balkans, Baltic areas, Russia, Ukraine (adminstered by the Polish under the Mongols), Afghanistan, Uzbekistan, Turkmenistan, India, Tibet on and on and on. The Mongols also invaded Japan. So this type of helmet and other parts of the armor branched out. On the other hand There seems to be a divide between Slavic and Main Land European Armor typology. A real east west divide perhaps due to the types of horses they were using and the distances they had to cover.

I seriously doubt that the type of horse being ridden to battle or the distancees travelled had any infliuence at all on the type of armour worn.

I'm willing to bet that the weight of metal armour worn by Turkish or Mongolian heavy cavalry is more than that of a knight in full plate harness.

Got me on that one... I am merely suggesting it. Has anyone done a study of the real weight of armour related to the horses being used? Or were the weapons they faced the prevailing factor? The folks comming off the steppes, Middle East and the Japanese used smaller horses than the large war horses of Europe. Also something to consider is how can you compare different cultures at different time periods use of armour. Are we comparing a Mongol from 1230 (Mongol invasion of Europe) to Ottoman heavy cavalry from 1370s (Invasion of the Balkans) to a French knight from 1500 (pre Pavia), Polish or Hungarian Hussar from 1500 (Poles vs the Golden Horde) and a Samurai from 1600 (end of Sengoku Jidai/Japanese Civil War)? Thats a span of 400 years with the major oponent of armour comming from non existent to readily available matchlocks on almost all sides.