I mentioned "factory authorized replacement stems" earlier, but find no factual evidence that Sasieni offered such a service (like Dunhill).
Barling had a complete refurbishment department. I suspect that such was a common practice to keep one's clientele happy. But the only way to know that is to see it mentioned in the company's literature.
The point about replacement stems is a good one. Whenever a seller claims the stem on a vintage pipe to be "original", I automatically discount that claim, unless there is something, such as a unique shaping like on this Barling Quaint:
that is non standard. There's really no way to know that a stem is original. In the case of Sasieni, the problem is magnified by the fact that the collectible value can vary widely, based on the nomenclature on the stem.
Catalog illustrations are a good guide, but not absolute for shape, as these pipes were largely hand finished and shape varied from pipe to pipe even within the tolerances of matching to a model pattern. However, in the case of the 4 Dot that Dave put up, it's not just the profile that's off, but also the positioning of the dots.
I've also seen the later "Specially Selected" reissues from the 1980's being sold as pre War pipes, But I don't remember if the copying of the old "fish tail" logo era pipes extended to the COM stamp as well. Also, The reissues didn't have a patent stamp.