4 ms·The first two digits of the serial number gives the years since 1960 of the revision for HP.by blattimwind 7y agoThe first two digits of the serial number gives the years since 1960 of the revision for HP.ChuckMcM 7y agoHmm, well then it would be 1999, first two digits are 39.bdavis__ 7y agoi would expect any HP RF test equipment from any age to be fixable and usable (worse case, perhaps new vacuum tubes!)