I was looking at this Slingy snare on Ebay and with a bit of investigation it looks to be a Hollywood Ace model which I have been told came in a 3 ply shell.
Having a look at the underside photo it looks to me like a solid shell.
Did Slingerland make solid shell snare drums with "rapid strainers"?
I looked at the Slingerland catalogue and the Radio King of that era came with a "3 point strainer".
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140289955601&ssPageName=ADME:X:RTQ:US:1123