Probably half a dozen Urich M1s have passed through my license for various reasons over many years. Only two were transferred to me, #820 and #812. It was evident to me that these numbers were his chosen numbers for registration. I recall that the usual info was applied to both sides of the receivers and had no reason to believe that it had not been done by Urich. Interesting to entertain the views expressed here and Urich's comments.
Having acquired my first legal, live MG in 1970, by the '72 or '73 I was aware of the issues faced by parties interested in the legal manufacture and registration of MGs from a few conversations with Doug Offinger who had pushed ATF to assist in determining how individuals and licensees could both legally import and manufacture live MGs from those left unregistered during the '68 Amnesty and how to proceed to make and register new receivers. The GCA '68 which included the Amnesty, but did not address or affect the federal laws governing manufacture and registration of live MGs for sale and possession by individuals. So, many issues were raised by him and a number of other persons and ATF responded with the early protocols for registration that existed until May 19, 1986.
One of the issues was markings. Newly manufactured and remanufactured receivers were required to be marked by the maker wether an individual or a licensee. There was no direct oversight or inspection by ATF of products for compliance with manufacturing requirements. If there was it was rare and unusual. The issue of marking by producers of registered MGs was fairly widespread and controversial for a simple reason which was that they felt that the markings "scarred" the MG. Reproducing accurate original factory markings was very popular with a number of makers for a variety of types of MGs and having to put the makers ID on the receiver was considered defacing the gun. As a result, placing the maker's ID in an out of the way location became very popular. Remember that ATF personnel NEVER saw the hardware, which continues today, and an inspection by ATF of the FFL/SOT licensee focussed on paperwork compliance and not hardware compliance.
So, many makers would put their ID info on the receiver under some removable part, done as small as possible or in as inconspicuous a place as possible. Urich did the same but had the clever idea of putting the info under the rear sight that was removable. As far as a "violation" of ATF regs, this is as insignificant as it can be and remains so to this day. It is just not a legal problem with any legally registered MG. The variety of ways to mark MGs is large. The details of markings have been revised with stricter application and depth requirements over the years to where they are today, but enforcement of incorrect marking placement, means or size on registered MGs is an extremely minor issue compared with myriad other compliance issues with the insanely twisted regulations and definitions created by ATF for administration of NFA after the GCA '68 Amnesty. For years compliance was up to the desires and inclinations of the makers, and the extent of their ambition to make money or produce quantities of hardware or other dreams and the industry was pretty wild and indifferent to and interpretative of much of what ATF required, not to mention outright fraud of which there was more than enough.
Another point is that alterations of or additions to the markings, within the law, on registered MGs as time has passed to make them more "authentic" has increased a lot. There are lots of examples of this with quite a variety of MGs.
As far as buyer/collectors not knowing that Urich's products were not "original" factory MGs, that's just part of every collector world. As they say, "get over it". When he was producing his guns there was no effort to conceal their origin, or claim false legitimacy, and it was easily determined with minor inquiry, as with many other newly manufactured and registered MGs. These MGs were recognized as reproductions and it was expected that they could vary In quality from comical to absolutely accurate depending on maker. Just the difference in the cost of a repro compared to an original factory gun made it obvious. Fraudulent or inaccurate representation of the provenence of an MG is nothing new whether deliberate or out of ignorance so caveat emptor always applies. The intricate hierarchy of social/collector's status from possession of an original or a repro has always been alive and well in the MG hobby and Urichs guns have been part of that for a long time. However, these days, and with the internet, the minutiae included on the scale of collectibility with Thompsons is daunting so it was inevitable that it would be applied more and more to Urich's guns as time passed. But, in my opinion, his guns must be assessed in light of the prevailing culture of the MG collector world during the years they were made, as much as a Savage or Colt would be, and, more importantly, not unfairly assigned implications of legal liability that are not germane or valid.
It's a longwinded post, but the observation above that Urich might be trying to "distance" himself from his guns for legal reasons or any other is absurd and insulting to him. He did MG collectors a great favor for harnessing his enthusiasm and skills to produce as many Thompsons as he did and deserves kudos and recognition for that. Personally, I feel indebted to and highly appreciative of all the people who knowingly or inadvertently nurtured this hobby, even from prior to WWI, by their importation of MGs and parts, who brought back MGs from the wars, who manufactured and registered MGs for the eighteen years it was permitted, and even to treasury and then ATF personnel who did their jobs fairly and effectively as best they could and those still doing it despite the long, continuing and amazing thick, curdled consistency of the cultural and legal resistance to what we like to do. And there has been a lot of luck, too. FWIW