Mine is 4828xxxx and is from March 92 according to ilovemyspeedmaster.
I see you have a diferent dial, compare the S and R from Speedmaster, that should date yours before between 90 and 91 according to the book Moonwatch only
I got the ebook for 20 eur. But in the UK the book costs “only” 112 GBP
Thanks, am really happy with the watch and not overly concerned about mismatched lume, It happens and I have seen worse, like Heuer 980 divers from the early 80s. Take mine for example....