Any experts know what this seat is. It was fitted to a 1989 K100 RS SE as per picture below. It has some numbers 5253 what then looks like a 1 then 4534970 on the base. I can't find anything like this listed but wondered if anyone here knows where it came from and if it could be an original BMW fitment ?

Original BMW part #52 53 2 308 237 (black).
The SE version did have a dark blue, which then have another part #.