Seems they made a few different versions of the QuadDoubler that were rotated in different directions to accommodate different systems (according to
Amiga Hardware Database):
> available in different pin orientations - the QuadDobler model number BSW2001004950 installs parallel over the A3640
Different part #s I've seen (
mentioned here, and on
Sonnet's page here and
here):
BST-40F - Centris 610 (and presumably Quadra Workgroup Server 60/20)
BST-50FA (BSW2001004950) - Quadra 610 Workgroup Server 60/25, also Amiga A3640 & "X-Calibur"
BST-50FB - 100/50Mhz Quadra 660AV, 700, 900, Centris 660AV
BST-50FC - Centris 650
Presumably by looking at Mac models you'd be able to determine how they're rotated to fit in the chassis.
As far as rarity - good luck. Saw one at beginning of last year, and one at beginning of this year, and that's it. I missed getting those, been trying to get my hands on one for a long time.
Attached are some images I've collected of ones in the wild over the years, maybe they'll help your search:
From an eBay listing 2018 Feb by
taddy-izumi
From ??
From someone on reddit a few years back:
From Quadra 700 listing 2019 Jan:
This old thread now since lost in 68kmla transition had some images of an attempt to put one in a Performa 630. I believe this was
@johnklos. Notice the addition of spacers, and the "spectrum engineering" label:
Mentioned by
@nglevin, this is actually the Newer Technology Quadra Overdrive.
According to
this post on AF, it came in a regular and PLUS version, the latter having L2 cache (!).