I scoped Mike Acre's site but he has nothing on that model. Suspect it may have been built by Remington if as old as you say. Can you post a picture?

Here is a link that might be useful: Chainsaw Collectors Corner

here is the link... I've tried searching the web for the manual to download and even gone to deere.com support website but virtually impossible to find one.
Not sure what kind of air filter it uses foam/paper/???

You might try looking in your local library for this manual by Intertec Publishing - "Chain Saw Service Manual, 10th Edition, cover models through 1998". ISBN is 0-87288-705-7. It does have three pages of info on the 50V and similar JD saws. No info on the air filter though.

The 50V/60V series was made by Echo. There's definately an air filter. It's right under the top metal cover.

I'd take it to your local Echo dealer and see if they have an air filter. It would also be a good idea to replace the fuel line. (it's probably shot by now)

Chain Saw Service Manual, 10th Edition, cover models through 1998". ISBN is 0-87288-705-7.

Yes, I've tried looking into this manual but unfortunately there is no indication where the air filter.
When opening up the top metal cover there were couple of wire which connect either to the trigger switch.

Correction: The air filter cover is on the left hand side right behind the starter. There's a metal cover with a thumb screw.

Go to the site in the second post and search all the Echos until you find one that resembles yours. Start with CS-451VL because I bet that's it.

Now go to echo-usa.com and go to web parts search and enter that model number.