I found the on-the-drops.blogspot document to be a great reference for this bicycle and the impact it had on the market, and the sport itself. Your efforts and insight are much appreciated.

I have acquired a Vitus 979 last year, and started a restoration process as I had a great frame, but it had a frankenstein equipment not matching the 80's or the type of bike at all.

This document was essential to my pursuit, and I used the method provided to decipher the actual year. My serno started with E063xxx (one letter, followed by 6 digits)...

I deducted that this frame was E (A->80, B->81, C->82, D->83, E->84, F->85)from 1984... but then the 06, would indicate a 1986, and the 3 would be March, the xxx indicating the number of bikes produced that month...

So there was a problem with the deciphering, the letter AND the first two digits could not be the year. . . If not, what was the letter representing ?

I proceeded to look at all Vitus bikes I could get a serno from, and ebay was a good source for that. What I could not find was any other letters used in the serno besides: A, E, F and I...

So the next question if not the year, was what is the letter representing ?

.. and here is what I believe based on the answers I got from people owning 979 with serno starting with letters E, F, or I: E stands for English Bottom Bracket, F for French Bottom Bracket, and I for Italian ones.

So what does the A represents ? Simply the first production frames that were produced with a french bottom bracket and before they produced other types of bottom brackets (this is my hypothesis, and I am still looking for validation on that point).

Now, onto the remaining digits... Sorry Peter, but I do not see how the two next digits could represent the the production year and the following representing the month of production within the year.

Simply put, a friend of mine purchased a new Vitus in 1988, and the serno is already E103xxx. The deciphering approach was breaking down again.

Now onto the month coding. First, as mentioned in a post earlier, you need two digits, so it should be 01, 02, 03.. to 12, or if they use the next two to represent double digits months (from 10 to 12), it would drive an extra digit in the overall serno size (9 digits for bikes produced in Oct, Nov, Dec)... I have not seen any serno on a Vitus 979 frame with more than 1 letter (A, E, F or I), and 6 digits (123456). Never 7 digits, meaning that 3 months of the year could not be encoded in the serno.

Now, let's assume that the 3rd digit in the serno is the month, it leaves only 3 digits to represent the production number in this month. What do you do for frames 1000+ (again, the production volume was over 15,000 (possibly 17,000 frames in 1984, which means you have many months were more than 1000 frames were produced)... So this is another reason why this encoding approach does not work...

I believe the deciphering is more simple:
first letter A (1980-1981), then E, F and I in later years as additional bottom bracket types were produced, and the 7 digits represented just the sequential production number. . .

To find out the actual year, you need to know how many frames were produced each year... You can approximate this knowing that within each each between 1981 to 1984 between 15,000 (1981) to 17,000 (1984) frames were produced, and 10,000 frames were produced in 1980. . .

So based on the above, my bike frame was likely to be a 1984 bike frame. .

Happy to go over the above in more details, and with additional supporting information... and if you have a response to that, I am more than happy to reconsider. . .

Sincerely,

Christian