Patent numbers were used in the markets for which the patent had been granted (i.e. a UK patent number was stamped on a pipe sold in the UK, and the equivalent US patent number was stamped on a pipe shipped to the US); moreover I believe such pipes were marked only during the period the patent was in force. There may be exceptions to this practice, but it was the case often enough with other manufacturers that I suspect it was the rule.
In this case it looks to me like the stinger matches patent GB213201 applied for by Joel Sasieni in the UK on January 29, 1923, which was the equivalent of patent number US1513428 granted in the US on October 28, 1924. Since at that time patent life in the UK was 14 years from application, and in the US 17 years from grant, UK sold pipes would have been stamped with the patent number through early 1937, while US sold pipes would have been stamped through the fall of 1941. Note that in the UK it was possible to apply for a 7 year extension of the patent (which would have extended the expiration date to early 1944), but I have found no evidence that Sasieni attempted this.
In sum, the patent applied to the stinger, not the dot; the stinger is original to the pipe and matches patents granted in both the UK and the US; and the lack of a patent stamp suggests to me that the pipe dates to a time after these patents expired, i.e. 1937 or later. Given the fishtail logo the likely range is approximately 1937-1946, with war-related disruptions making a date of 1937-1939 more likely.
Incidentally, if you want to see an example of a pipe stamped with a UK patent number, see Ashdigger's one dot here: http://pipesmagazine.com/forums/topic/sasieni-one-dot-w-script-w-patent-w-stinger-pic-heavy. It's clearly marked with the number for an earlier UK patent that protected an earlier version of a stinger: GB150221/20. The 150221 on the shank is the patent number of course, and the suffix /20 denotes the year of the patent.
