From what i gather, the engraving would kill the value to a purist collector. Well, ok, they would want the original box and all associated paperwork and tools with it. That one does not fit the bill there! But, it is in great condition and as a shooting gun, it would be great. Ignore the initials. It had value to someone at a previous time. You paid a price well under shooter grade anyway. Also, I have not seen diamond targets selling for anywhere close to $100, nowdays!
I look at modified guns as guns that someone in times spent money to make them useful for their needs. I'm not interested in changing what was valuable to them (well, mostly). I have a Registered Magnum that was shipped with an 8 3/4 inch barrel. It now has a 6 inch barrel, the front Patridge sight has been rounded, the hammer has been made cockeyed, and pearl ruby eyed steerhead stocks added. I paid a lot more for it than the original owner invested in it and I'm sure I can sell it for more than I paid for it. But, I would not think of trying to make it back into the original condition. I replace the stocks for shooting, and enjoy what I have!! You have a very nice Model 19, enjoy it and don't let those little bitty initials bother you any!