It was asked on another forum and I thought Mr. Taffin might be able to help. It was noted that his 7 1/2" Colt Flattop Target wasn't in the museum. Does anyone know what became of this gun?

I thought this was an incorrect statement, but I just checked my photos from my first trip to the Museum in 2004, shortly after it opened,
There was no original Colt Flat Top there, but there were 2 customs converted by Houchins, a 5 1/2" (with the quick-draw stud), and a 7 1/2". Plus the Number 5 of course.
Elmer was said to have owned the only original Colt Flat Top.

WHEN I WENT THROUGH HIS SIXGUNS AFTER HE DIED I DID NOT SEE THE 7-1/2" .44 SPECIAL FLAT-TOP. HE NEVER SAID HOW HE GOT THIS SIXGUN BUT THE FLAT-TOP WENT OUT OF PRODUCTION BEFORE THE .44 SPECIAL ARRIVED. I ALWAYS WONDERED IF IT WA S A .44 RUSSIAN WITH THE CHAMBER ALTERED OR IF COLT PUT TOGETHER A PARTS GUN FOR HIM. HE WANTED MUCH BETTER SIGHTS ON HIS SIXGUNS THAN THIS FLAT-TOP HAD.

Thank you, this answers why it could have been the only 44sp at the time. I wonder what became of it?