This is most likely XK2S1-100717498 or maybe the last digit is 'A' instead of '8'.
Unfortunately it doesn't really tell you much, apart from the fact it's a round-nose 850cc Mini saloon of base spec (ie not deluxe/ Mayfair trim). I have spent years compiling a database of numbers and still (with hundreds of records), I can tell you that very little matches up with the various numbering systems and it is not easy to specifically date a bodyshell as the serial numbers seem to be quite random at times. You think you're getting somewhere then an original car shows up with a serial number miles out from the others...
Anyway, the number changed to a SAXX.... VIN in mid 1980, so you know it pre dates this, although, again, the riveted-on plate can show SAXXL2S1 while the gutter can show XL2S1, on the same car.
If the last digit is 8 and not A, that dates it to early 1980 as that's when they dropped the A.
If you still have an FE number on the left hand front inner wing, or a body number on the slam panel, that can tell you roughly when the body was made but again, no official records were kept and I've seen wildly different number ranges on cars from the same year. If the car is relatively complete, there are quite a few week/ date stamps in various components that are useful.
I think your early 1980 guess is right and it will have been one of the last 850cc cars.