Olds Leadpipe specs
Below are the leadpipe specifications for the Ambassador and Special trumpets. It appears to me that the labeling for the Special (on the left) may have said Super + Special, but the beginning of Super was cut off. Note also that at the bottom end of the leftmost dimension line, there is faint writing that may also say Super. If the Super and Special shared the same mouthpipe taper design, that would be a very interesting!
It appears to me that the measurements are taken every quarter inch down the pipe.
It is interesting to note that the Special (and maybe Super) begins smaller and tapers more gradually than the Ambassador. Both have a three inch receiver pipe measuring 0.375 inches in diameter. That is a bit difficult to reconcile with my horns. It seems that 1 3/4 inches is closer to the actual length of the receiver. Perhaps these dimensions were used to manufacture the leadpipe, after which a precise length, approximately 1 1/4 inches, was cut off the end.
After this, the Special begins at 0.325 versus the Ambassador at 0.340. The diameter of the Special expands over a span of 14 inches to a final diameter of 0.454″. The Ambassador leadpipe begins at a wider diameter of 0.340 inches, reaching a final diameter of 0.458″ in about 12 1/4 inches. Both of these lengths extend beyond the actual leadpipe into the top sleeve of the main tuning slide.
I have attempted to reconcile these measurements with my 1947 Special trumpet and my 1954 Ambassador trumpet. Interestingly, if you pull the tuning slide out the prescribed 3/8 inch, and start your measurement at the beginning of the narrowed pipe after the mouthpiece receiver, the above tapered lengths take you almost exactly to the beginning (top) of the curved portion of the tuning slide on both horns.
For the Special, the crook of the tuning slide is 0.455″ in diameter, a one-thousanth increase over the end of the leadpipe. Then, after the tuning slide, it expands again to 0.456″. The Ambassador does something similar, with the leadpipe ending at 0.458, then the tuning slide being (it is hard to read) maybe 0.4595, and then the final bore at the end of the tuning slide at 0.460 inches.
It is also interesting to note that the rate of taper is not completely uniform in either pipe.
I would be very interested in hearing from anyone who is able to take these measurements on an actual horn, to confirm these interpretations.