I sell a lot of N.O.S. Tjet chassis. It always amazes me how people spin the back wheels and examine the numbers and letters on the chassis bottom and top plates. Some tell me the numbers are better, lower rather than higher. Some tell me the opposite. Some tell me letters are the best. I know why the letters and numbers are there, to identify the many mold cavities used in their manufacture. I know about solid rivet vs hollow rivet, I feel solid rivet were made in the USA by machinists and moldmakers where tight tolerances were a must. The hollow rivet chassis were mass produced in the Orient and tolerances are less stringent. My question is this, what number/letter chassis do you like, and WHY???