Update: Briar Blues has an excellent Castello dating guide on their website called the CASTELLO, DATING & INFORMATION.
In the beginning -maybe the pipes were stamped Mi Reserva my reserve. This Reg No has nothing to do with shape numbers, but is merely the Castello company trademark. From early Castello pipe advertising from the Wally Frank and later Hollco Rohr companies it says the pipe comes with Vulcanite stems.
However the photo's appear to have pipes with Lucite stems. To our knowledge no one has yet seen a Vulcanite stemmed Castello with the faux diamond logo inset. Castello castello pipe dating guide occasionally put rhinestones in the mouthpieces, just to maintain it's value as a trademark.
The black dot logo is used on Castello pipes with white Lucite stems. Big Line - stamp used from - Replaced by Great Line, although still used on huge pipes.