My condolences on the loss of your Dad.
If you have your heart set on that Marbles mount, you have your work cut out for you as far as locating one. Marbles has been out of business for a LONG time, and they made great stuff, and most all of it is highly prized by collectors. Your only options are to watch ebay & gunbroker, I doubt you'd even find one in an old mom & pop shop out in the middle of nowhere. Last Marbles see thru mount I saw was on ebay, about a year ago, for a Savage 24, and I stopped bidding on it when it hit 60 dollars, just to give you an idea of what the stuff might go for.
What you might want to consider, is a Weaver 'pivot' mount and rings. While not made anymore, a pivot mount and rings are more easily found on ebay for a 760, and they would be 'time period' correct also. Actually a much better setup for a 760, because with see thru mounts, your cheek tends to come off the stock when you have to look through the scope. With the pivot mount, you can simply swing the scope off to the left to use the iron sights, and it does return to zero, I have them and use them. In this manner, you always have a good 'cheek weld' on the stock, wether using iron sights, or the scope.
If you are interested in the Weaver Pivot Mount for a 760, that part numbers are, #49220 for the pivot rings, and #162 for the pivot base.
If you don't know what a pivot base is and how it works, let me know, and I'll post some pics for you of a slug gun I drilled and tapped and put a pivot base setup for a Remington 760 on.
