wvcollector:
Your dad has a .38 Military & Police Model of 1905 1st change manufactured between 1906 & 1909 in the serial range 73251 to 146899.
In 2006 the Standard Catalog of S&W gave the following values: Good $225, Very Good $285, Excellent $385.
Be aware that this model lacks the internal hammer block safety in use since 1944. If dropped it could fire, so leave the chamber under the hammer empty.
It also predates heat treatment of cylinders, so stick to standard velocity lead loads only. No jacketed, semi jacketed, PlusP or +P+ ammo.
The 158 grain round nose lead cartridge was the standard at the time, anything similar should be OK. The reference on the barrel to U.S. Service Ctg is to the .38 Long colt cartridge that could also be fired through this gun. The .38 Special is a stretched Long colt case, lust as the .357 magnum is a stretched .38 Special case. S&W didn't want to stamp 'Colt' on their barrels. Colt of course returned the favour!
The Model of 1905 is the ancestor to todays model 10, aftermarket K frame grips will work, internal parts will be different as there have been many design changes over the last 100 years. Numrich Arms are a good source of second hand parts.