These are only partially German. in B+W literature "R" means red in colour correction (CC) filters (Green, Blue, Yellow, Magenta and Cyan being the other colours, in English) - e.g. in CC015R.
KR stands for "Konversion Rot", German for "CR", red conversion filters (though most people would consider their "red" a vivid orange), KB is the blue "CB" counterpart.
Neither a R nor a KR filter will be a skylight filter per se, pure colour shifting and correction filters need not block UV. But as skylight filters are defined to be UV blocking filters with a additional KR/CR 1.5 tint, you'll often see the latter on skylight filters. Before you use a found CR1.5 filter in UV rich settings, make sure yours is also marked "Sky", "skylight" or the like - on plain studio use versions you would need a separate UV filter...
YMMV, filter nomenclature can be a brand specific mess, and while few makers made the actual filters (and even less made filter glass) just about everybody who made cameras, lenses or accessories felt the urge to distribute some filter series under his label and with his own nomenclature variation - wherever they (deservedly) felt that their glass and frames weren't unique enough to warrant yet another filter brand they invented a new naming system. For example, some companies sold CC filters with plain "R15", "B05" etc. engravings - others may have sold CB/CR filters with similar inscriptions...
