Yup...
That is a Buckheimer holster - as mentioned by Denster. I just remembered the same design was made by Safety Speed, during the same time period. I cannot remember who made it first. I remember it because this one is mine - I casually collect old cop holsters as well as old cop guns.
The revolver is more than likely a brother to this one: a Colt Detective Special. Mr. Selleck's has a silver colored metal medallion in the upper grip, signifying the grips are probably wood, rather than the plastic I have. Wood was the original material, then Colt used plastic from 'after' World War II to about 1954 or so, when they resumed using wood. The shape of the butt frame and the grips was pretty constant, however.
I know this will cause some modern shooters both immediate horror and perhaps some sleepless nights, but the cutaway trigger guard was rather popular for a number of years. The serious objection to the practice was based on possibly bending the trigger guard against the trigger, making the revolver inoperable as a firearm.
Caution: Old Guy History Lesson follows: There was a time prior to collapsible batons and various chemical sprays, when plain clothes officers employed a sidearm as an 'impact weapon' for those instances when a suspect was resisting arrest not amounting to lethal force. Note the chip on the bottom of the left side grip on my revolver.
The cutaway trigger guard was not considered so dangerous as to preclude the use of such revolvers. In those days, 'safety' was more an issue of personal accountability and responsibility, and not so much an issue of 'doo-dads'.Here endeth the lesson.
The sample Detective Special (sometimes pronounced 'Dick Special') shown was originally sold in the Los Angeles County area. I bought it used in 2009 or 2010 or so for my 'cop gun collection'. It bears up to its heritage as a Colt Double Action revolver by being so out of time it won'd index and fire reliably. Due to the modifications, I have every reason to believe it belonged to a local peace officer in the Los Angeles area; but no 'actual proof'.
Salty Dog: You are correct about trigger shoes on NRA Bullseye competition guns. I used one or two myself in my day. However, most Bullseye pistols were never holstered, so the 'danger' of pulling the trigger in such was minimized. I do remember several holster makers issued warnings about using trigger shoes on sidearms (usually always revolvers) in their holsters.