Interesting. Hope this helps us out I some way. I get so fed up when there are sales and I can't take advantage...not just firearms, but mail ordering mags even.
Normally there is a phone number listed for them in Gunbroker. You might have to look at the seller's profile/info.
I bought a 1951 from them early this year, and just called to give my credit card number and find out where to mail my C&R.
Tapco Gen IIs worked great in my Mini-14 Ranch today.
The only minor hiccup was chambering the first round, but after that it was smooth sailing.
I'm done spending $30-40 per mag. I'll have no issue using these Tapco mags for $8.