Many thanks to Ron Luxemburg, nrcapes, Dr Zarkov and whizbang for the serial numbers and other details of their C5s which I’ve now added to the C5 Registry and bumped it to the 7th Edition. As usual, the new entries are highlighted in blue and to keep the file size down I've only shown an image of the top part of the list in the image below, however the orange link above will take you to a jpg of the full version.
Dr Zarkov’s C5, serial # 2 3902 8, indicates that it was only sometime during or after the 2nd quarter in 1978 that Celestron changed from their ‘Q nnnn Y’ format (where Q = the quarter of production, nnnn = a sequential production number and Y = the last digit of the year of production) to a temporary format before they abandoned any date indication and changed to the ‘5nnnnn’ format (where 5 = C5 and nnnnn = a sequential production number).
It looks like the temporary format may have just dropped Q the quarter indicator to become ‘nnnn Y’ with nnnn, the sequential production number continuing in sequence from the old format before it was re-zeroed when the ‘5nnnnn’ format came in as we now have in the Registry two 1st quarter 1978 C5s, # 1 3585 8 and # 136588, then Dr Zarkov’s 2nd quarter C5 with # 2 3902 8 and then 4 C5s with the new temporary format, # 4165 8, 4190 8 and 4311 8 all in 1978 and # 4350 9 in 1979 which gives the following sequence of production numbers: 3585; 3658; 3902; 4165; 4190; 4311 and 4350.
With regard to motor numbers, whilst Don is right in that when looking at a single C5 in isolation, the motor date only gives the earliest date that the scope could have been made (assuming of course that the motors haven’t been replaced at some later stage) because Celestron could have purchased 100,000 motors in 1975 and be still using them for scopes produced in 1982, this is where I think there is value in recording the motor dates along with the serial numbers as it then gives an idea of how quickly Celestron’s stock of motors was turned over.
Unfortunately, when we get to the scopes produced after 1979 which have serial numbers with no date indicators we don’t really have much to go on other than motor dates and the odd data point provided by a scope that has a verified purchase date (and even then there is no telling how long it might have sat in the dealer’s stock).
As ever, all contributions, clarifications and corrections gratefully received and remember – we love pictures too (and they help to detail the smaller changes over the years such as whether phillips or hex head screws were used for the secondary adjustment.)