You lucky duck. You look to have the mark 3 with the revised height adjust (the first to have the proven plastic tooth detents) as well as the 8" rear wheels.
Total quality. Body looks in good conditIon.
I once had the mark 2 and it often hopped out of it's height setting, leaving a mini crop circle. A known problem addressed by this design.

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!