From my searching I believe this is a EH-500 Skylark. But I can't id the year and actually I'm not positive about the instrument either - just going by pictures that others have posted. Serial number on back of headstock = 17872. Late 50s - early 60s? I haven't found anyplace that has serial numbers of the electric lap steel guitars, just the acoustics.
Also if you have ideas on how to figure out a reasonable value for the guitar I'd appreciate it. I've found listings of sold guitars but no price. The guitar is not in pristine condition, but aside from the tone know (which doesn't do anything, I've had it in to someone who had no luck fixing it) it works. It looks like all of the parts (including the case) are original but I'm not an expert.
Thanks.