Klause,
Once again you've done an incredible job of finding an obscure treasure from the past! This is a pipe about which I know almost nothing; but that won't stop me from making a few remarks.
First, I think if you look closer you'll see that the stamping says "G Cotton & Son", not "G Collins". This is corroborated, by the way, by the Trebor mentions in the various US Tobacco issues from the late teens/early twenties available on Google. In several cases they mention bundling promotions with John Cotton product.
G. Cotton & Son was founded by the father of the John Cotton we all know, George Cotton (1749-1831). Old George had eleven kids, of whom John was the last. One of John's older brothers (also named George) went into business with old dad, and helped perpetuate the company he had established in Edinburgh about 1774. Interestingly enough this family business was separate and distinct from the tobacco shop and snuff manufacturing business eventually launched by John. Only many decades later did the two businesses come together, when the later owners of John Cotton bought out the later owners of George Cotton & Son. This happened some years before your pipe was made.
As for Trebor, as huntertrw notes the patent was issued to Baron Cohen in 1912. Here the trail gets murky. But before we try to follow it up, I can tell you that Baron Cohen (1864-1951) was listed as a tobacco manufacturer by the age of 27 in the 1891 census; that he was in the cigarette manufacturing and importing business with his father, Woolf Henry Cohen (1838-1920), and two other men until the end of 1893, at which time he exited the partnership; and that he is listed in subsequent censuses as active in the cigar importing or tobacco dealing trades.
More obscure is the progressive ownership of the Trebor pipe. It continues to appear in industry brand listings through 1957, after which is disappears, never to return. Over the approximately 36 years for which I have data, it is shown as owned by Cohen & Co. in 1921, by Trebor Ltd and Cyril Arnold Ltd from 1927-1929; by the same two entities plus Baron & Co. from 1932-1938; by the same three entities plus L. Hill & Co. in 1939; and after a gap in the listings reappears as owned solely by L. Hill & Co. from 1949-1951; finally from 1953-1957 the name is owned by Trebor Products & Agencies. What does this alphabet soup of entities mean? Without a lot more digging I can't say. Several are clearly related to Baron Cohen the man; others are more obscure, bobbing up on the waves for a few years before sinking without a trace. Cyril Arnold Ltd, for example, only appears in the London phone books from 1925-1930. Similarly brief appearances are true of most of the other companies.
More interesting is the question of where the name Trebor came from to begin with. This is just pure speculation, but there was a long time candy giant in England called Trebor; it was founded in 1907 and the brand was eventually absorbed into Cadbury in the 1980s. A book has been published about the history of the company (see: http://www.thetreborstory.com/). I haven't read it, but there was a long standing symbiotic relationship between tobacco and confection retailers that spanned most of the 20th century. It seems possible to me that Trebor (the candy company) might have financed/licensed/distributed Trebor the pipe. But to be clear: that's pure speculation.
In any event, Klause, another beauty. I hope you enjoy it!
Regards,
Jon