Old Quintron/Glenayre GL exciters and TXCs come in a diecast
hinged-lid box that is ideal for building tube audio gear in. If you
can't sell them as working boxes you should gut the cases and market
them to the tube audio guys. You want the three -pocket one with the PA
and spring-mounted Hartzell (yes, the prop people) VCO ideally for a
preamp.