This has been a difficult series to collect. Despite what catalog value suggest, this is an eye opener. A somewhat neglected series but a tough one to assemble.
Struck in between 1941 to 1943 during the Japanese occupation, the Provisional Government has authorized the Federal Reserve to issue coins. These coins are exactly the same as the Japanese aluminum coins that were issued at that time. In particular, when Osaka mint had to make drastic option to reduce the weight of aluminum, these Federal Reserve coins also followed suit. While it is not clear where these coins were struck (either Osaka or in China), they definitely are of the same planchets.
There is only nine coins to this series and catalog value wise, there doesn't seem to be any reason why they can't be completed for around 200 dollars. Turns out this is just an indicative and it does not reflect reality. Three difficult coins are as followed (from slightly difficult to very difficult): 1942 5 fen, 1943 1 fen, 1943 5 fen. As of why 1943 coins are hard to find - who knows. Maybe Japan was facing a situation where aluminum had to be rationalized. However that doesn't explain why 1943 1 jiao coins are rather common...
The holy grail of this series is the 1943 5 fen - which I had to sell off some of my coins to purchase this. Unfortunately cleaned and perhaps paid way over catalog value but I'm certain this is one coin that doesn't appear in the market any time soon. The last time I saw it, it was about two - three years ago.

As of how long I took to hunt down all the coins, it took a good five years (!) The rest of the collection can be seen here:
http://gxseries.com/numis/china/china_federal.htmPlease feel free to show your coins as well!