Vielleicht hier mal durchgraben?
http://www.cbcadmin.com/ado16/
Laut Wiki hat der Einkolben-Schwimmsättel, Minis haben Zweikolben-Festsättel.
http://en.wikipedia.org/wiki/BMC_ADO16
Dieses PDF spricht aber auch von Zweikolbensätteln beim MK I:
http://www.the1100club.com/1100clubmember…rake-clutch.pdf
Darin gibt's zwar einen Hinweis, das der MG Midget die gleichen hat, aber der MK II ab 1967 hatte die oben erwähnten Schwimmsättel, die kein anderes Auto hat. 
Zitat aus dem verlinkten PDF:
Zitat
In 1967 shortly after the introduction of the mk2 range, calipers changed to a
single swinging piston design. Last available OE part number 37H7217 (RH),
AP 4832-719; 37H7218 (LH), AP 4832-720 This necessitated changes to the
discs, the front hoses, the rear check valve and the rear wheel cylinders. No
other car was ever fitted with this caliper, and even the pistons are only
common to a Saab 95 V8. The calipers have not been made for many years,
although at one time AP marketed a kit which consisted of new parts which
could be fitted to an existing frame, SSB2620 RH, SSB2621 LH. Existing
calipers can be reconditioned, and the pistons have in the past been
obtainable as remanufactured parts, eg from Brake Engineering. Original
parts are scarce, and no conventional supplier lists them now. The AP part
SSB2609 (OE part no 18G8327) now LK12609 which is listed as a "repair kit"
is in fact the rubber seal kit for the pistons and has no practical use without
new pistons.
Alles anzeigen
Da wären zumindest Teilenummern. Viel Glück.
Grüße,
Andreas