Hiya Mate , :)
It's nice to hear that you like them too . As far as I know, the coating on the top E and B is Brass - although they can be obtained with either brass plate or the usual tin plate 'plain' strings . I only discovered this second fact by accident when my string supplier sent me a packet with a sticker on denoting that this pack contained tin plated 'plain' strings. The problem with ordering through an intermediary, being of course - that for years, I did not know Thomastik offered both !
The supposed brass plate certainly ages nicely like real brass , with a warm patina - and matches B.K.P gold plate pickups very nicely. This I mention, because it verifies that the Thomastik coating is therefore not yellow chrome. Along with the silk wrap at both ends of the wound strings, the whole effect is one of being a 'class act'. :)
As for my usage, I settled on Thomastik 'Swing' Flatwounds, in a 12 gauge. I have a very light touch, now play with a medium pick ( for clearer dynamics and more 'air' ) held close to the tip, so although Thomastik 14's are very easy to play on a 'Lyre' tailpiece guitar, the 14's were giving me more of a straight ahead warm Jazz tone with push on the tip of the notes, whereas the 12s betray / portray more detail in the vibrato, false harmonics - and minute subtleties of pick and fretting hand 'special effects'.
They are my all time favourite for Jazz playing - and ( as you mentioned ) the 'Be-Bop' roundwound strings have a GORGEOUS piano like clarity and resonance. I eventually went with Flatwound, instead of one guitar with each type - as my 'Schtick' is a very smooth "After Dinner" solo presentation, when even minor string scr@pes and 'zings' would detract from ( trying to ) make the listener almost forget to breathe when listening, to seduce with the materials on hand - and not just play. :)
Thanks for reporting back Keven ! :D