Hi, I own #177 (originally sold by a dealer in USA) and #920 (originally sold by a dealer in Canada) and both are in quite original condition. Both have the same seat, Carlisle Arrow tire, mag wheel (Morris I have been told, not Lester, as is sometimes suggested), brake system, adjustable shock which has yellow lower paint with some blue stripes on coils above, graphics, and Astro-like black turf carpeting. I cannot see any changes.
#177 has had by previous owner a radio install, antenna, and a side light added. It also has two Vetter pop-up vents that look factory to me, but it has been suggested to me that they must have been done by an owner. I have seen these vents in the exact same place on another TP, so a bit of a mystery to me.
Based on my two, I would expect that yours would have been the same as lower and higher numbers. Maybe they figured that they got it right from the very beginning and no changes were needed. Also, changes take time and cost money I suppose, so keeping the same production steps and suppliers for parts etc. would have made sense. Your question is an interesting one. Mike