That is a lovely rifle and I've no problem with the Silas Allen attribution but a word of caution on attributing unsigned NE rifles... nearly all of them were made in Worcester county, a relatively small geographic area, and there is nothing like the variety of style that Pennsylvania rifles exhibit. I would be very surprised if all the prominent makers didn't know each other. It is also very likely that most of the wire work and engraving was not done by the "maker" but by itinerant specialized workmen - hence engraving styles and wire work styles are almost impossible to pinpoint. Nearly identical work is often seen on rifles signed by different makers. There are a few differences that can at least be associated with certain makers... Henry Pratt sometimes used a very distinctive trigger guard and Welcome Mathewson had a very distinctive, archaic, long hand rail butt shape and distinctive horse head patchbox. However, items like Lindsay's contention that only Martin Smith used brass triggers is simply wrong.
The Allen family were one of the very first NE makers to be mentioned in print. Charles Winthrop Sawyer mentioned them 100 years ago in his "Firearms in American History" (published in 1910). Silas Allen is also listed in the first edition of Gardner, published in 1936. As a result, his is probably the most commonly seen name among the famous Kimball-Teft fakes.
There is compelling logic to suggest that, unlike Pennsylvania rifles, most NE rifles were made for the volunteer militia rifle companies that were quite popular in New England. I remember this theory being advanced by Frank Klay who probably had (or has) more of them than anyone else. I only saw his collection once, but I seem to remember he had something like 50 of them. I have owned two with militia "rack" numbers on them and remember seeing a pair of rifles that both had the name of the company engraved on the patchbox. This being the case, there is a reasonable chance that an observant collector can find several identical rifles... I have a signed Henry Pratt and once had its unsigned identical twin. I have no way of being certain, however, that both were made by Pratt. I have never seen a flintlock NE rifle that would not accept the standard government .54 caliber rifle bullet, with the exception of a John Mason I currently own that will accept a .69 caliber ball! The bulk of these rifles were supplied to a market that literally had nothing to hunt that could have required such large bullets. Central Massachusetts is supposedly 70% forrested now but was only about 15% forrested in 1825. In 1842 Massachusetts overhauled the militia system and ceased to enforce the requirement for militiamen to provide their own arms. Only then did the state provide arms to the remaining volunteer companies (and some of the rifle companies had to accept muskets since there was a shortage of M1817 Common rifles). Percussion NE rifles, which arrive on the scene at precisely the same moment, are hardly ever larger than .45 caliber and most are between .38 and .42. These are often fitted with both target and hunting sights reflecting the popularity of target shooting and the absence of large game.
I also harbor a sneaking suspicion that many of the flintlock NE rifles were actually made in Birmingham and imported whole or in a semi-finished state. That is, however, a very un-tested theory. Next week I will be in Birmingham doing some research on the Ketlands and I hope to turn up a little more information.
The "Rifles" chapter in George Moller's "Massachusetts Military Firearms" is also very good, although now out of print. The Lindsay book has to be appreciated for its illustrations but anyone who has tried to read it will realize it is a hopeless hash of captions with no pictures and pictures with no captions. Merrill didn't write them in any case, they were contributed by the owners. Some are reasonably good, at least in the context of 30 years ago, while others were wishful thinking even then.