AFAIK, Interstate no longer sells the U-series batteries make by US Battery, but switched over to Mexican- built batteries of a better design (they say) in 2010ish and call them, eg, GC2-XHD instead of U-2200 at 232AH.
So that makes it seem the 1A is indeed Jan '01, which is ridiculous--you would hope!
On the battery there should also be a sticker with the last charge date on it and when the next recharge must happen. With any luck you should get the sticker saying within a month of when it was built on the side stamped date. You also get a punched hole date for when you bought it, which has to do with the warranty at the dealer's.
In any case, IMO just poke an hydrometer in them and see what it says. My GC2 XHDs were at 1.300 SG when new, and I can still get them there with a proper re-charge. If you can get yours anywhere above 1.280 SG say, in all cells, I would not worry about whatever weird special order things went on back then.