Eric Elman is offering for sale: <snip> 3. GB Synchron front & rear brake calipers. Used but very good condition. I bought for my Geoffrey Butler but they just don't look appropriate on that bike so I'll be using Universal 68's. $30.- shipped.
I don't have a dog in this fight, but they do have a special place in my heart. These critters, also available with Altenberger dress, are 1960s dual pivot brakes. Compared with the current hi-zoot stuff, they are huge, but the principle is the same. I put one set on a first-series small-wheel Moulton, and they definitely improved performance enormously over the precursor steel side pulls. For the Moulton, the side-pull-like cable run was critical, and they fitted the rear where I couldn't get some other brakes to fit.
So, they are homely enough for a Sears, were used on some lower-end Raleighs during the bike boom of the early 1970s (think Gran Prix or Record level), and I found them quite satisfactory in use.
Full disclosure: Eric and I have done a few transactions, but I sure don't have an interest in this one. I still have one pair.
harvey sachs
mcLean va