Originally Posted by
Mad Dog
Sayak, go nuts, you won't ruin any collector value.
The pictures you have posted are of a model 99E wood, not F. The E in 99E stands for "economy" and they were usually made with less extras than the others, like the round counter and tang safety. The E would have no round counter and a lever safety. If it's just an R then it's an inspectors stamp but if you've got a partial serial number I can give you a date on it.
As for what the "original" sling studs and swivels on an F looked like is nothing, they never left the factory with them on it. If you wanted sling swivels on them after 1960 you put them on yourself on most models like the F's and E's.
No worries about purists on the rifles made after 1960, the collectors are mostly after the pre-59 rifles which were hand checkered and built much stronger. After 1960 they started to use stamped parts and functionality started downhill. Although a few calibers like 375 Win, 22-250 and 7mm-08 still bring the big bucks in the 99's made after 1960 due to the rarity of them.