Well, that is interesting. Here's all I know about them.
But they fit the A, B, C, E, & F versions of BW transfer cases, and usually the early-in-the-alphabet ones are the early versions, which would be the BW1345 instead of the BW1356. But I have no idea what they do inside the t-case. But they are cheap!
Gary, AKA "Gary fellow":
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Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI