Are you sure this isn't a Heathkit as is or an Altec custom done by Barzilay? I mean it looks too professional/extensive to be a re-work of a 101, plus (and it's a big plus to me) it's a double bass reflex (DBR) tuning which was virtually unknown (and still is to great extent) at the time except in professional circles and serious DIYers that read a variety of audio magazines.
For sure, it's the first I've seen from back then beyond its inventor George Augsberger's early '60s JBL cab. There's software to design them now, but back then it was strictly empirically tuned, at least at the DIY level.
GM
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