I should know this and I'm a little embarrassed. Did these guns have the wide triggers like the Trooper MKIII? Got my eyes on a 5", can't tell from the photo. Thank you ladies and gents. Love ya, mean it!
I have no idea on time line, but as I recall the early fixed sight Mark III models like the Official Police Mark III had narrow Service type hammers and triggers.
The trigger was narrow and I "think" grooved, the hammer was narrow and grooved instead of checkered.
In order to simplify production this started changing at some point, first the hammer was changed to the wider checkered type, then the narrow Service type trigger was changed to wide.
Not certain if this is exactly pertinent to Your thread/question, Chief $.02, but I feel that it's worth mentioning.
FWIW: You can change a Mark III trigger using newly cast, aftermarket parts, or simply check Gunbroker/Ebay, etc, for a parts kit, taken from a (court ordered) & destroyed revolver.
I bought such a parts kit a few years ago, because I wanted to change My early Mark III Trooper's trigger from narrow/grooved, to wide/smooth.
That kit was well worth the money expended, as I also received the entire gun, (minus frame), supplying Moi with extra parts, should anything ever wear out on one of My Mark III's.