Following up on a thread from a few weeks back, I finally did speak this week with Barry Witcomb at Witcomb Cycles in south London. As had been guessed, the last two digits of a serial number are the year of constructio n and the rest of the number is sequential, based on the order the frames are completed. He's got good records back to about 1962. The frames were built in-house from about 1959 or 1960 so there's spottier records for the frames before 1962.
As for the frame I picked up a couple months ago, numbered 926772, it was built by Phil Lippett (spelling?) and completed on May 9, 1972. I've tried searching the archives using a number of spellings, but can't find mention of Lippett. The frameset was then exported to Riverside Cycle Sport (in Riverside, California? -- if so, not far from where I was growing up at tha t time).
And for the gentlemen who suggested that a 1972 Witcomb had been in the presence of Sachs and Weigle, I can now clearly say Whoo Hoo! YES, it's remotely possible that e-RICHIE was sent to buy fish and chips for Phil while he was brazing up this frame, and subsequently learned a great deal from sweeping up Phil's filings. That will boost resale value! If I actuall y planned on selling it, that is. Still, the potential for eBay hype is there , taunting my twisted sense of humor.
Seriously, the bike will be built up and ridden. Maybe not right away, but soon. A refinishing is in its future, too, and I've sent off my order for original transfers to Barry -- who's even got the "Custom Built by Phil Lippett" decals, too. I'm right pleased all around.