I was looking through a bunch of foreign coins I have, and I found something weird about this one. There is an 80 stamped over the 40. It may be hard to see from this scan, but I was wondering if it was some sort of error?
I think you have it backwards - it is likely a 40 countermarked over an 80. But it's hard to say for sure because it went both ways depending on what the date at the time was. Some of these coins were countermarked 40 over 20 and some 40 over 80.
According to Krause, most dates are valued around $5 in VG. I don't think this coin would grade that high. But there is one date, (deosn't have a date on it really but that's when it was issued ) the 1835 SP - it is valued at $40 in Good.