"After serial number 1,000,000 numbering was restarted, the V prefer was added and numbering started over at V1.
Early Lend-Lease British guns were marked 'United States Property', or U.S. property.
But, at the time of the V-1 serial number change, the British guns used the same serial number block as the U.S. .38 Special Victory Model."
Not after 1 million, just before. S&W's numbering machine only went to six digits, so they went to 999999, then to V1. The V (and later the S) was stamped on all frames when the frame was made, then the rest of the serial number added later (that is why the V is sometimes separated from the number). Reportedly, they planned to use an A, but when "V for Victory" was suggested they went with it. The Military always called it simply the M&P Model.
The USP stamp was used to maintain the legal fiction that Lend Lease items were sold to the U.S., then loaned to the Allies. Since one cannot loan what he does not own, those guns became officially "U.S. Property."
Guns made for England and later other Allies in .38 S&W were called the Model K-200 or 38/200 by the factory; technically only the ones for the U.S. were ever called the Victory Model, leading to a lot of confusion for folks reading information from factory records. However, they were all numbered in the same series, the normal M&P series up to 999999, then the V (or VS) series from there on. There were no separate number blocks.
Jim