Someone please help me ID this particular part.(highlighted in yellow box)
Thank you.
I believe that is an early ACE stock. Its not made anymore.
I believe that particular part is the hinged butt plate - with the whole stock appearing to have been lifted off an FN MINIMI. With the folding mechanism appearing to be copied from the Galil - but inverted.
I think Nacho is correct, nevertheless, as I believe that ACE used FN MINIMI stocks.
Hinged butt plate, I don’t ever recall seeing any Galil/R4 para-stocks with them but then again I haven’t seen every Galil under the sun. IIRC, FN had a version of the FAL para-stock with one as well as later with the Minimi.
Never new early ACE stocks came with them, that is pretty wild.