Need some help on 3572.50

Hello everyone,

I hope that some veterans here could input on this piece. I've done the ref check on ilovespeedmaster but the caliber doesn't seem quite tie (i.e., 861) 😕

Well of course, based on what I am seeing, this piece is a c.1997 T Dial, yet the movement is 1863. I would have thought that all T dials would have been 863s while the SL dials are fitted with 1863. I'm confused or am I getting the transitioning periods wrong.

Much appreciated if someone here could shed some light to this piece 😀😉 I'm really keen on this piece with the nice patina.

Attached some pictures for your evaluation:

This is the best 3572 - tritium dial and 1863 movement. IDK how rare, but they are the best. I had two of them over the years.