OAC  (Ovenaire) Model OSC 35-42B
(26-0040-01) 10.000 MHz "Precision Crystal Oscillator" 
Serial No. 36600-3661

 
That unit is a TCXO - 
+/- .75 ppm for +5 to +60C, 
.75 ppm/year and 5 ppm for 10 years.  
Since the unit is obviously older than 10 years, 
it will be interesting to see if where the frequency is now.
 
Looking at the bottom with the pins at the top, numbering left to right:
1.  0V & ground 
2. +12VDC @ 15 mA 
3. +5VDC @ 10 mA
4. RF output (TTL compatible)
5.  VCXO input (+/- 10VDC gives -/+ 6 to -/+ 12 ppm)
 
Typical phase noise is -100 @ 10 Hz, -110 @ 100, -120 @ 1k & -130 @ 10k.