Never heard of them before... but I don't typically pay much attention to equipment that didn't make its way onto the NP.
Setting aside my bias, one might consider researching "strick-tainer" in the various NYC propaganda, Railway Age, and perhaps Jane's Freight Containers (the entry for Strick in my '70 edition of the latter publication is not helpful). For what it's worth, the listing for them didn't change at all between the July '66 and October '68 ORERs, showing 100 of them, numbered 262001 to 262199, dimensions of 20' long, 8' wide, 13'9" on a 48" 5th wheel. Door openings are listed as 7' 5 1/2" wide and 8' 0 1/4" tall (no notes about a side door). Apparently, the NYC containers were designed to be paired together and moved as a 40' unit, which makes me think the peculiar supports showing up are part of the chassis.
The only other operators of 'Stricktaners' that I've found thus far is REA, who listed a grand total of eight... not exactly a common sight.
Sam