Mr Eick,
the grips on bluekouki86's gun are not original. They are post 1968, as they lack the un-checkered diamond around the grip screws. They also appear to be Goncalo Alves rather than walnut, so 1967-1980.
mikemyers:
N514xxx places your gun in the period 1978-1980. Red ramp inserts were common by that stage. The target hammer is .5 an inch wide, as opposed to the .375 of the standard 'semi-target' and the narrow prewar triggers.
The target trigger is grooved and flared to the sides, pretty much filling the width of the trigger guard, as opposed to the flat sided trigger with or without serrations found on service guns.
Target grips are larger, designed to fill the hand and make access to the hammer easier (well I think thats the idea, it works with my big paws. Service or 'Magna' grips are smaller so they are less likely to catch when carried and may make double action fire easier for those with smaller hands. Mr Eicks photo in post 17 shows service, target, service & service grips.
3Ts is the abbreviation for target trigger, hammer and grips. They are rarely seen on service grade guns such as the Model 28. My model 28 from 1968 has original target grips, with semi target hammer and trigger.