How can i tell what year my bike is? There is no sticker but can i use the serial number to find out?

ok so its a 2000 rm 125 but how come the forks arnt inverted. Besides that it all looks like a 2000.
the guy must have put an older front end on it.
I looked at your name and thought we were talking about YZ's. ok, now RMs I can talk about for sure.99 and up and has inverted 96-98 has usd normal uprights