amongest the 12 ,or so watches/works i'v found,1 is marked rolex& gruen together,any idea what this is,& who made it for who?

i recently purchased a storage trailer 'full' of 'NOS',& used antique & vintage watches,jewlers cases of parts,several 'boxes' of nos, high end stems,crowns,hand sets,misc boxes of new& used parts in packages,a 'FLEXO-crystal" 12 drawer case,full of NOS,packaged crystals(about 1400),a watch makers p...