Headless:
Indeed, so I researched further...
Supposedly the “D” series of serial numbers were used on models 10, 12, 13, 14, and 45, where serial numbers in the “1D” series were used on models 64 and 65. Then those in series “2D” through “7D” were used on models 10, 12, 13, 45, 64, 65 and 547.
Thus Smith & Wesson’s propensity to put different models into a single serial number range and mix them up has sometimes caused mass confusion. Their practice at the time was to make frames, serial number them, and then at some future time pull them out of inventory and make them into different model revolvers. Such a mess we have here…
The model 64 is nothing more or less then a model 10 (.38 Military & Police) made out of stainless steel. It was introduced in 1970, and marked on the frame inside the yoke cut as “MOD 64”. The number “101” on the yoke (swing-arm dealio)
is an assembly number and of no consequence to us now.
The “1D” serial number series didn’t start until 1976 at serial No. 1D 1. The “D” series ended in 1977 at No. D 999,999. (not D 99,999 as I first thought). Obviously S&W did make some models 64 and 65 in the “D” serial number series, my research book not withstanding.
With all of this figured out I would estimate that your friend's model 64, serial No. D 552,xxx was made around 1973, and should be safe to use with Plus – P ammunition, although extensive use of some kinds of such ammunition might accelerate wear.
Hope this finely answers your questions.