Perry, The 3010A prefix identifies that date it was made. It should also have a 10811A marking. The resistor value is for applications needing precise EFC. Usually found in HP 5065A, 5061A, and 5061B. If it also has a 60109 marking it has slightly better short term stability at one Tau. Specs are otherwise the same as any 10811A. There is no outer oven! Since the design is a complete departure from the original 105 oscillator it makes sense they issued a new part ID. The 10811A started to go into the 105A and the 5061A and 5065A after the 105 style oscillator was discontinued. Cheers, Corby

Corby wrote: > The 3010A prefix identifies that date it was made. Specifically, it identifies the "series" of the product -- the date the last revision to the product was adopted. The "3010" part is the encoded date for that particular series (10th week of the 30th year past HP "year one"), and the "A" indicates that it was manufactured in the US. [I've forgotten what "year one" was for the Instrument Division. It was 1960 for the calculators -- I/D may also have used 1960.] Best regards, Charles