That is what is known as a Waffle horn from a Kustom cabinet. I have a few of them myself with original ALtec 418's in the cabs. I also have cabs with the original Altec 421's in other Kustom cabs as well as JBL D-130' and D-140's as well. The cabs with two 418's and a siren horn sound tremendous as PA mains with Peavey 1 18 subs. I also use a pair of old EV TL606 cabs with 421's loaded in them for subs as well. Kustom made great stuff as I have a huge amount of it and it all still works today and sounds better than most of the new stuff made today.

Bart

This is a part of my Kustom Kollection from Chanute KS. I have one of nearly every color, they came in 7 colors.
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