Not a skeleton key, purchased 1970's I can't find the key... might you know how to "Pick" the lock?

Lockpicking tools are are series of little thin metal rods with various shapes at the ends, designed to fit most simple locks. They aren't easy to buy these days because of laws against selling them. You can try bending paper clips, or keys from other small locks. You might be able to get an antique shop to 'rent' you a box of random keys. A locksmith can get it open in 2 minutes, for a fee of course.

Skeleton Keys - Kennedy Hardware LLC

The Keyway will help a lot to identify. There is another site that has a lot of antique or old roll top desk keys. Will see if I can locate.
Can you describe or provide a photo of the keyway?