That time interval unit is kind of cool. I've bought 2 5245Ls at hamfests and paid around $50. Shipping is kind of a killer on those but maybe he'll take a reasonable offer on his make offer.
If you had a 5257a transfer oscillator plugin, that thing will count to 18GHz (yes, that's a G). Not too shabby for 1971 vintage.
There was also a DVM plugin available.