joaovictorio:
Your gun was produced in 1981. If the hammer is fully exposed then it is a Model 37 .38 Chiefs Special Airweight. If all but the tip of the hammer is concealed by a hump on the back of the frame, then it is a Model 38 Bodyguard Airweight.
Neither Model was rated for PlusP until 1997 when they switched to the larger K J-magnum frame.
The general rule of thumb with these older guns is to train with standard pressure loads, fire once cylinder of PlusP for familiarization, then carry with PlusP. It will not blow up with PlusP; but will see accelerated wear.
jasper275:
Your Model 67 .38 Combat Masterpiece Stainless was manufactured in 1977. The serial number is 16K5901, the other numbers are assembly numbers, used to track parts in the factory. They have no meaning after the gun was shipped.
Your Model 686 Distinguished Combat Magnum Stainless was manufactured in 1985. AJR0417 is the serial number, the other numbers are assembly numbers.
There is a recall on this model. With some magnum ammo the primer can flow back into the firing pin bushing, locking up the cylinder. Under the recall S&W will pay shipping both ways and install a new firing pin and bushing. If the gun has already been modified there will be an M stamped near the model number under the cylinder yoke. If it has not been modified and you wish to have this done, call S&W customer service and they will send you a shipping label.
Sealevel:
The Model 17-4 4 inch heavy barrel was introduced in 1986 when the taper barreled Model 18 was discontinued. The 17-6 with the full lug barrel was officially released in 1989. with early guns using up the old stock of heavy barrels.
Your gun was produced mid to late 1988.
Slimbo:
if there is no letter prefix to the serial number then you have a .38 Military & Police Model of 1905 4th Change manufactured between 1927 & 1930. Serial range for those years was 500000 to 630000. If the grips are original and have a silver medallion, then 1929-1930. If plain walnut then 1927-1928.