I have read comments regarding rifles, including the rifle M1icon, with red bands painted on them for identification to indicate non-standard ammunition, that have returned from the United Kingdomicon. The implication is that these rifles were Lend-Lease, but I rather doubt the U.S. would have sent the standard rifle that was needed to equip the Army and Marine Corps. I suppose the current C&R writers have documents that show the rifles were provided under the Lend-Lease act, and you might want to research the recently published books available on the subject. Apparently the Remington manufactured rifle M1903s were originally contracted under the Lend-Lease Act.

As to the scabbard, the various embossed markings you describe are probably inspector stamps, which was usually the inspector's initials, and the final inspection was located near the manufacturer's marking that usually included the year of manufacture. I rather doubt that the British would have had any requirement for a rifle scabbard for Home Guard use. However never say never.