It seems that Samick made most of the Korean Arias... but there have been other companies like "Sumer" (at least they claim to have made some).
Anyway, the most obvious difference for a post Matsumoku TA is that the bridge design changed. The post Matsumoku bridges can not be locked in place anymore (don't think that TonePros were the first to get that idea
).
If the TA you're looking at has stoptail, you can also tell by its spacing, if this is Matsumoku or not (the post Matsumoku ones have a wider spacing).
There have been a couple of Japanese made TAs in recent years. They were not overly expensive, but imho not exported. This is one thing you should be careful about when looking at newer Arias... for example a current model "PE Inspire" for the Japanese market is made in Japan... while the "PE-Inspire" for export (with identical specs) is made in Korea (from the serial number Samick). The list price of the Japanese guitar is twice of the Korean models and most eBay seller will try to blur the information on manufacturing location to hike the price.