Originally Posted by TandemGeek

The drum brake looks to be an Atom drum brake that has been modified and that is missing the face place... which is where the "ATOM" branding was placed on those things.

Frankly, if you're doing a mild restoration to make the bike rideable I'd forget about replicating the original brake control configuration; it's sub-optimal at best. Instead, I'd suggest running your front & rear rim brakes (the original sidepulls or, better yet... some newer standard reach calipers) off of dedicated brake levers (one each), bearing in mind that it's the rims that are really lousy when it comes to brake efficiency even when matched with fresh brake pads. For pleasure riding on tame terrain in dry weather, no worries. Just don't take on any steep terrain that might demand "good" brakes.

As for the drum, does it still work? The first order of business would be making sure those drum brake shoe linings are still viable, bearing in mind that they may have some asbestos in the pad material, i.e., be careful when working with them and wear a respirator if you need to de-glaze them and the brake drum.

If the brake shoe linings are shot, you can probably have them relined or you may be able to find some NOS parts with a little bit of searching. They're rare but available and occasionally found on hand in places that specialize in bicycle & motorcycle restorations (I believe the Atom like the Arai drum was originally made for use on mopeds).

As for operating the brake, I'd suggesting using what most tandem teams using bar-end shifters have used for the past 15-20 years, a thumb shifter mounted on either the captain or stoker's bars.

If you'd like to keep some level of dual control brakes, search for a pair of Dia-Compe 287T brake levers. They have dual-brake cable controls and route the cables out from under the brake lever body. Again, I'd suggest a modification to the original configuration if you go dual control by running your front rim brake off of a single lever and their pairing your rear rim and drum off another.

You can run dual rim and single rear drum... it'll work. But I prefer to see a bomb-proof front brake installation that provides riders with intiutive performance vs. trying to optimize the front & rear rim brakes to operate effectively off of a single brake lever while giving up the other to a drum brake that can't stop your tandem... it can only slow it down. Moreover, if you get the "balance" wrong on the rear rim + rear drum, you'll just skid the rear tire and, well... that's not good either.

Just my .02.