What does 500m stamped on bottom of silver piece plan? ...

I just this minute moved to Montana. There...
Answers:    It would be helpful to know what the jib is. Is it jewelry or a serving piece of some sort? Also are there any other results with the "500m"?

If near are other marks next to it, my first guess would be that it is a date mark. More information would oblige to put it into context.

Edit:
Actually, 925 is sterling, not pure silver. I have never see a 925 mark next to an "m" after it. It can be followed by an "S" for silver, but is most often on it's own.

I am baffled by the "500m" engrave. If that's the only inscribe on the piece, it is probably not a date mark. There are several obedient, free sites online that you can look for the mark, it will purely take some time to click through the page. I've given some links in the sources. Good luck!