Hello again.. In some things I picked up was a NIB what appears to be a crystal calibrator for some type of Military gear. On the bottom is the following info. 250 KC OSC. 506-6215-904 MOD.2 Bailey Crystal oven code date 4/56 Uses a pair of 5749 tubes. Wonder if anyone can tell me what radio it is made for please? Thanks.. Merle W1GZS