If you want to really splurge on a house reference, have I got just the thing. I should get rid of my Stanford Research Systems FS725 Rubidium standard. It was used continuously for about one year back in the oughts in one of our (my previous employer) off-shore mfg sites. It has seen little use since then; I fire it up about once a year for some sort of test, but my time-nuts days are behind me. This box has Option 3 (18 outputs - all you can add) and it does not have a scratch on it.
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If you are interested, please contact me off list. Thanks...