Republic Of China Fat Man Dollar Y-329.1 - Real?

Last one for the day, Will try to get my hands on a scale in the next few days.

After some research mine appears to have a standard reeded edge so I dont think its the Y-329.1 & is most likely a Y-329 if genuine.

I have received a large collection of asian / Chinese coins. I unfortunately have no knowledge of the coins. They were purchased from an estate in which the collector had owned a coin shop in the 1980's & 1990's. They had said he sold the majority of his collection before his passing. I will be posting quite a few more Chinese coins.

This coin was in a envelope marked "Republic of China Y-329.1"

I was wondering about the authenticity of this coin as well as date / variety info & approx value. Majority of coins have been in brown paper envelopes for who knows how long.

I was able to test on my sigma metalytics machine and showed as silver. Diameter of the coin is 38.9mm.
Does not stick to a magnet.