dongle
That one is going to be difficult to value, it it helps I recently paid $450 for a none working Uranus calculator watch and fitted it with a Armitron module to at least have a wearable watch with a working time/date display.
Obviously retrofitting it with a working module would increase the value, the 1, 3, 5 button layout would suit some modules, Uranus automatically springs to mind but also the Hoyt message(?).