The CDNN grips are not for the early(150 series)Security Sixes! They only sell grips for the newer model(151 and up!)Security Sixes!
I would recommend that you watch eBay auctions for some Herrett's "Shooting Stars" wood grips for the(150 series)Ruger Security Six! These were made for both the(150)and the(151 and up!)Security Sixes and are very nice looking target grips, that are styled very original looking, to the "Classic" design of these early Security Sixes! The Herrett's box for these grips, will be marked in large(Bold)letters, as follows:
1)150 series, will be marked RSS(Ruger Security Six)and, Ruger Security Six will also be shown on the box(In very small print)!
2)151 series, will be marked RNSS(Ruger New Security Six)and, Ruger New Security Six will also be shown on the box(In very small print)!
3)NOTE: On both of the above Herrett's grips, if no box is available with an auction for these, remember to ask the eBay seller, to look on the inside of these grips for a sticker that will either read RSS or, RNSS?
I used to own a(150 series)Security Six and I did the above and found a set of these Herrett's "Shooting Stars" grips-and, my Security Six looked very handsome indeed with these! Although these grips don't come up on eBay everyday, I have seen them to appear from time to time, on a regular basis!