This gun probably ended up in England initially, and then went to war, along with thousands of other Thompsons. With some strange twist of fate it wound up in Denmark after the War.

McGuire's factory probably figured, its going out of the country, and its going to war, it will probably never come back, so why not.  And now 57 years after the war, this number on a Colt receiver surfaces again.

ABOVE S/N 7886 IN DENMARK

LEFT S/N 7886 IN IDAHO.

 
EDITOR'S NOTE: THIS IS WHERE I LOVE TO DO A LITTLE DETECTIVE WORK OR IN THIS CASE FONT WORK.  THE THOMPSON IN DENMARK IS A SAVAGE ARMS MADE GUN.  THE MODEL MARKINGS AND SERIAL NUMBER WERE MARKED BY SAVAGE ON AN UN-SERIAL NUMBERED RECEIVER MADE BY COLT'S. HERE IS HOW TO TELL. LOOK AT THE IDAHO TSMG NOTE THE MARKINGS:
MODEL OF 1921, NO 7886 (NOTICE THE COMMA AFTER 1921)
(NOTICE THE LOOPS OF THE NUMBER EIGHT WHICH ARE THE SAME WIDTH TOP AND BOTTOM) THIS IS THE TYPE FONT USED BY COLT'S.)
VS  
MODEL OF 1921 NO. 7886 (NOTICE NO COMMA AFTER 1921)
(NOTICE PERIOD AFTER NO AND THE LOOPS OF THE NUMBER EIGHT. THE TOP LOOP IS SMALLER THAN THE BOTTOM.) THIS IS THE TYPE FONT USED BY SAVAGE.
WE ALL KNOW THAT SAVAGE USED LEFT OVER COLT PARTS DURING THE BEGINNING OF THEIR PRODUCTION INCLUDING, IT SEEMS, RECEIVERS. NEAT STUFF. NICE JOB GORDON!