Lens serial number

I have managed to buy two nifty 50s on ebay, both good condition, both work well, so how to choose which one to resell. This seems logical to me, that the serial number on the lens mount would give an indication of date of manufacture, but is it?
I would sell the oldest one if I knew that the one with the lowest serial number was 'it'.
I've searched threads and read FAQs, but did not find an answer there. Apologies if I missed it.

Start at this thread, link in #2 response.

https://photography-on-the.net …&highlight=lens​+date+code

John from PA wrote in post #16434619
Start at this thread, link in #2 response.

https://photography-on-the.net …&highlight=lens​+date+code

Thanks John

The 50s have an eight digit code. Eek! I guess I'll keep the first one that I won.

I would not keep a lens based on it's age. I have had 7 Mark I 50's in the last year, and kept one for myself.
I put it on my 50D, and then I MFA each one against a focus chart. The one that needed the least adjusting, had the fewest flaws (internal dust), and gave the best images is the one I kept. I couldn't have cared less when it was made.

On our way to Flori-duh on Saturday for some winter sunshine!! I can't tell any difference between the two 50s image quality wise. I'll be selling one of them soon.

I couldn't tell the difference either in IQ, I went by my MFA numbers. The one that was closest to 0 for the MFA adjusting is the one I kept.

Where in Flori-duh are you going?