No idea, but I loved these speakers in 'ab' form (too shrill toned in the original version) and they're perfect for smaller rooms in a near to mid field environment. The B139 in ABR form flopped about too much with vinyl, but come the digital age, these then old boxes sprang to life in a small room and the very slight 'hollow character' of the B200 bass unit (in all the 70's boxes using it) was never ever noticeable if they were heard singly away from a dem room wall-of-speakers. The foam grilles crumbled decades ago but cloth and maybe crude foam replacements may be got now. Back in the mid noughties I was offered a pair in good nick for seventy five quid. I believe they fetch a lot more than that now...
I think KEF chased sales and marketing too much in the 90's onwards, tailoring the sound even of some Reference models to stand out in a mass-speaker dem (the ones with 'sssssssooooooper tweetersssssssss' all but stripping paint I remember, but it seems nowadays, proper objective design prevails once more - thank goodness.