They won't be from Japan, Sanwa stuff probably isn't even made in Japan. Look at the link I posted after I edited it, Sanwa "copy"
http://au.alibaba.com/product/721233830-Copy-Sanwa-OBSF-30-Push-Button.html
A handy tip for anybody ever contemplating buying from China: The chinese do not sell products from other countries. Why? Because their tariffs on imported products is huge. All they do is export export export to encourage the growth of their own industries.
So the same company is selling some buttons as actual legit Sanwas and some as copies. If the ones they are selling as legit ones are a little bit more, it's not impossible that they are actual Sanwa parts. I realize 90% of the shit on Alibaba is not actual name brand stuff, but there are definitely sellers on there selling real product.
I've only seen a couple threads on the internet saying "I bought Sanwa parts and they were fake" and the parts were actually bought from a well known American website that people here would probably consider reputable. (the claims of the parts being wrong turned out to by false anyway)
Just for the hell of it I messaged the seller to ask about the parts:
ca1006401384(2013-11-20 01:36:36):
I noticed you list some buttons as "Sanwa Copies" and some as "Sanwa. These buttons are genuine Sanwa right?
cn1000360897(2013-11-20 01:37:01):
sanwa is original
cn1000360897(2013-11-20 01:37:13):
copy sanwa is china made.the price is cheaper
It's $36.50 for 10 buttons shipped. I'm almost tempted to order some and compare them to known legit Sanwa parts.