Yes, the white bar was used originally by Castello, but the US distributor carried a line of pipes names White Bar, thus Castello ( in the early years ) created the faux diamond logo for the US market. Once the White Bar brand or the distributor were changed ( I don't know which ) Castello offered both logos for the US market. The faux diamond logo is still offered to continue the "trade mark", but in lesser numbers than the white bar logo.
The Vulcanite or Acrylic stem thing is really interesting. On an early advert, for Castello, it stated the pipes had Vulcanite stems. Exactly how many of these pipes were made, I have no idea, or if it was misprint in the advert.
I think we need to remember that the earliest Castello pipes were "machine made" like Savinelli, Rossi, Stanwell .. etc. Then they changed to being hand made. Were some of the machine made pipes fitted with Vulcanite stems? The only people that would know are no longer with us.