The given date how? From an online SN database? Those are known to be inaccurate at times.
More information required.
Dealer information should be taken with a grain of salt and a year or two doesn't affect value. Why obsess about the exact year. More important that the watch is legit and in good condition.
I just like researching before stuff arrives.
Well as someone who owns a 3590.50 speedy, having zeroed in on that as the reference I particularly wanted to buy, I can tell you what I understand to be the case and I'm happy to be corrected if wrong. The transition to the 3570.50 took place I believe around 1996 and included an updated bracelet design which was the 1499 bracelet, different in style to the 1479 found on the 3590.50 (mine included). You can find some 'transitional' 3750.50 models with the 1499 bracelet that have a tritium dial with now yellowed lume plots before tritium dials were phased out entirely in 1997. These transitional models also came with the updated 3570.50 bezel insert that restored the accent above Tachymètre.
My speedy's serial, which begins 4829 is, based on looking the ilovemyspeedmaster.com date estimates around early 1994.
So, although not having seen any images of your watch, I'd be surprised if a 77x serial from 1999/2000 could be a 3590.50. If I'm looking at an original 3590.50 I expect to see as a minimum a tritium dial and hands, no accent above Tachymetre on the bezel insert and the 1479 bracelet.
It really depends what you wanted; for me these characteristics were some of the reasons why I was buying it so obviously had to be there. If you're just trying to determine exactly what reference yours is and you don't mind about anything else then it's of little consquence, especially the exact year of production.
In that case I don't know. Do you have a picture of the bracelet clasp?
What I do know is that there are 'transitional' 3570.50 models with tritium dials and hands that are in the 483x serial range, so to have a 3590.50 in the 77x range would seem odd. The box looks period correct for a late 90s speedy but the red card isn't necessarily what I'd expect to see from that same era but who knows what may have been put together by an AD when it was first sold or whether the box is an add by the dealer.
So the options seem to be that it is a 3590.50 but with service dial, hands, bezel and bracelet, and with a warranty card whose style is seemingly a few years later than the last 3590.50 for whatever reason. You could surmise it sat around unsold or forgotten for a few years before sale, but then why the 77x serial? Or it's a 3570.50 with original parts with a period correct for early 2000s warranty card and serial number that erroneously had the 3590.50 reference stated on it.
Is it going to bother you? Are you concerned about authenticity? If not then I wouldn't sweat it too much.
I'm not really understanding, what do you mean by authenticity? Was this described as 100% original? It's one thing for a watch to be described as "legit," because service parts are always legit parts. That's a different matter from original, and therefore collectible.
Are you wanting someone to tell you the exact year of manufacture, or weigh in on the originality of the watch?
