The '29, '47 and '51 appear to me to be MD. The single notch in the S/W corner of the MM of the '79 has been discussed as a possible broken punch and is very common for that year.
I considered the variety that coop shows but there are some large differences. The S in the known variety does not extend off the tip of the repunched S, it is back toward center top. I think the unknown ikandiggit shows is die fatigue.
I went to the coppercoins site and for this particular one there isn't a photo and no die markers listed. Is there another page?
I guess they don't have images of that one yet. I guess I got my information from the RPM book. The book lists three stages. A: Strong secondary mint mark EDS B: Medium secondary mint mark MDS C: Weak secondary mint mark. LDS No other markers listed. 8( Sorry.