Hello spiriteagle20 and welcome to the forum.
It looks to me that you've got a .38 Military & Police Model of 1905 First or Second Change (S/N's overlap between 1st & 2nd Change).
This is an especially cool heirloom made even better with your name being the same as the original purchaser (your Grand Dad). I would get a letter from Roy Jinks (S&W Factory Historian), but chances are it will have the name of the business that it was originally shipped to and maybe not your Grandfather (I'd do it anyway, you may get something interesting besides just dry info).
Until one of our resident experts chimes-in with more info (and possible corrections to what I've told you).
Left hand holsters aren't real common, but they can be sometimes found on eBay and GunBroker.
Here's a link to Roy Jinks (S&W Historian) Firearm History Request - Smith & Wesson