Robert Sussex

Hello, amongst the pile of spares that came with my 3a is what I assume is am early TR2 frame. It is aluminium with baby tenax posts, The posts screw right through the frame with a shouldered head and small nut on the outside of the frame so the peg is part of the screw. Is this aa unusual item? I wasn't aware that ali frames were available. It is in poor condition bent etc. but free to any member who could make use of it if wanting early authentisity. Best wishes. Robert.