Plus remember there is no one making any new sealed in the box versions. As temptation strikes people to open one, that dwindling number drops yet again. So are they worth more ? Yes then again no, because the value to a lot is a 20 round GI magazine. No different than one made a decade later and newer ones may have improvements. You'll have to wait if you want to get a little more from a collector of magazines and/or retro rifle builders. Remember that saying about the 3 prices, one to sell today, one to sell within a month, and one to just let the world know you own it. In between the first 2 is the tricky part.
Although, Everyone needs a triangle hand guard version of the AR/M-16 in their collection which the mags would display nicely next to. Retro and Vietnam surplus is drying up it it has been 4 decades and the DOD isn't releasing as much as surplus as they used to before it destroyed. leaving it as scrap metal. You can't go wrong with a classic.
If you want more detailed info posting photos here and/or in the retro forum at
www.ar15.com/forums/f_3/123_AR_15___M_16_Retro_Forum.html should help you with any. There is a special "appraisal thread" pinned at the top but it takes a little longer for people to notice the new post in it. Posting may also earn you PM from people offering to buy it. I think the retro crowd would like to see pictures of them , if for nothing else to add to the database of knowledge for any variations.
Also this post
http://www.ar15.com/archive/topic.html?b=3&f=123&t=577412 may be of interest to you.