The coin in the scan has the legend Xian ???? Zhong Bao. i cannot decipher the second (bottom) character.
Reverse is plain
Diam:33.8, 12.5g
Casting quality is very poor. The coin came covered in a black tarry gunk which was surprisingly easy to remove using a fairly powerful household cleaner.
I can't understand why anyone bothering to make a fake would do such a lousy job.
There is of course the possibility that it is a crude Annamese or Indonesian copy of a Qing 10-cash coin.
A fellow collector has informed me through the CoinTalk website that this coin is a privately cast Ham Nghi Trung Bao 15 Van, cast in Vietnam around 1885. He identifies it as Krause X # 21. I don't have this publication, so cannot confirm. If anyone can do so, maybe we can move this to the Annam section.
Krause Mishler SCWC does show a CRAIG 21 under their Annam listing. However, this is a 'phan' (cash) size coin ~ 23mm. The coin/photo is crude w/plain reverse. Obverse is described as "Trung bao"; struck under Canh Hung (1740-87). There's a Note: 'Trung' in this case, is the 9-stroke character meaning "heavy". All other uses of 'Trung' with respect to Annamese dongs refer to the 4-stroke character meaning "middle."
I'll send you a scan of the photo, it could be a lower denom. of the 15 Van type, the characters are similar on some but clearly different on others. KM does not show a 15 Van denomination at all (10 & 20 only). "Ham Nghi" characters appear correct on nicely executed coins of 1884-5. Phan coin is plain on Rx, a 6 Van coin has "Luc Van" on the Rx. None of these are crudely made. Additionally, I'm not finding anything in TODA (mostly earlier coins) that is similar.