Turkeystalker, you're reading of the law is correct. Several points though:
First, it's a basic principle of MA and US law (not withstanding zoning laws) that the law only says what you cannot do, or what you must do, but not what you can or may do.. Several members have said they've bought magazines like yours (preban) in the same way with no negative repercussions for themselves or the seller. It's anecdotal evidence, but the best confirmation you're going to get here.
Second, the MA AWB (until 20 July 2016) mirrored the old federal ban that expired in 2004 in letter and practice. Nothing Healy did on 20 July changed the definition of pre-original-ban ('94) magazines or guns. If the magazines you are selling were in your possession, or you know they were in someone else's possession, prior to expiration of the federal AWB in 2004 then they should be legal preban magazines, assuming you or pre=2004 owners were not LEOs.
Third, the lack of markings also indicates likelihood of pre-ban status. During the federal ban >10 capacity magazines were supposed to be marked for LEO use only. Many, if not all magazines, made after the federal ban seem to have markings now such as the manufacturer, serial numbers, even a manufacture date. It's probably not a rule or law that this must be done, but further evidence that you're good to go with shipping the preban magazines.
Fourth, regarding the incorrect answers you got from the AG Office (AGO). The MA AGO has been anti-gun for decades. Like most (all?) anti-gun organizations they do not know the current laws. MA (currently) does not have magazine registration so authorities have no way of knowing what magazines get sent into MA. The fact that the AGO lied to you means nothing, really; they dissimulate to MA residents all the time, they care even less about being truthful to an out-of-stater.
Finally, if this all is not enough to make you feel comfortable sending the magazines, then don't. My free advice (worth what you're paying for it) is not to announce your decision here, either way. If you say you did send them then there is a small chance the wrong spy might read it and somehow cause you grief, though I think that very unlikely. If you say you didn't send them then all the people here frustrated with the AG's latest shenanigans will tear you a new one for falling for the AG's FUD campaign.
p.s. To attach a picture directly one must be a paid NES member, so-called "green" members for the color of their username. The rest of us freeloading blackies have to use other hosting sites. Also, "blue" members are moderators, "orange/yellow" are dealer members, and red is the NES admin/owner.