2 of them go in an EML 500 synthesizer from the early 70's, in the sample and hold section, after the LM748, tied together by a center pin and an edge pin. The transistor in the schematic doesn't have an npn or pnp sign or any designation for that matter, just an arrow pointing from what looks like the base to the center, I'm guessing it's a unijuntion... Any ideas? Its a circular white package, with a black dome, e202 written in black letters.

 

May we see this mystery part on the schematic?

 

The E202 is an N-channel junction FET.
Some data here: http://www.datasheets360.com/pdf/-425082804961943338

 

The E202 is an N-channel junction FET.
Some data here: http://www.datasheets360.com/pdf/-425082804961943338

would that be the same as a j202?
https://media.digikey.com/pdf/Data Sheets/Fairchild PDFs/J201-02, MMBFJ201-203.pdf

 

There isn't much data for the E202 to go on but what there is matches so it would likely be a good swap.