It would be a real interesting dream / fantasy if the drivers (at least the woofer) were truly from a clapped out set of LS3/5a's (I know of at least 3 pairs of speakers rebuilt into different cabinets from that circumstance). But the mere writing doesn't establish that well enough and certainly the crossover is completely DIY and all wrong on surface. I have never seen the Linn Kan crossover so can't comment there but the B110's do not look like Linn modified (they added black silicone "spackle" additional damping to the cone and frame).
Unfortunately, there is no way to tell if the B110 drivers are LS3/5a spec unless they have some type of Rogers sticker indicating that selection or they were later versions from KEF with some identifying info on their labels (some listed as passing a test sequence) or have some frequency sweeps run on them if one knows the BBC selection criteria. However, just based on appearance, they do look vintage enough (discoloration of cone, surrounds and frame), my guess is 1978 or earlier (to 1975), a picture of the back of the driver and its date code sticker could help in production dates but not actual specification and selection for use in an LS3/5a. Before 1975 IIRC, the cones had the tinsel leads showing beyond the dustcap and entering the voice coil on opposite sides as compared to same side and below the dustcap. The pre 75 also had unpainted chassis frames as opposed to the black painted frames.
Likely the crossover is a homebrew version of perhaps one of the KEF CS1 or 1A crossovers that are many times used to DIY mimic the LS3/5a response in a less complicated crossover. If there was T27's there originally (as the mounting rebate may suggest), then these could have been modeled after either the LS3/5a in a more modern cabinet (heavier, thicker, undamped (?!), with rounded non-diffraction edges. A fairly common and potentially (sometimes) upgrade option but the speakers don't always come out better sounding. Also, the cabinet reminds me of the original speakers that Sigfried Linkwitz built when he originally came up with the Linkwitz-Riley style active crossover design for satellite - sub combos.
http://www.linkwitzlab.com/x-sb80-3wy.htm
Looks not nearly as deep however, but likely more typical LS3/5a type dimensions. Dig the single string free air mounting of the satellites, some suggest this is the ultimate in free standing speakers (shades of some BOSE 901's I'd seen at Pacific Stereo in the day - gads, did I just mention Bose and LS3/5a's in the same thread :nono::nono::nono
BTW, Falcon Acoustics still makes a crossover applicable for this type of DIY project and could make this yet into a LS3/5a type speaker if OP is interested and can source the T27's. Falcon also advocated making the LS3/5a speaker deeper (from 7 inches to 9 inches) to improve bass response without changing the midrange much if at all.
For whatever originally paid, and now for just the $20 bucks, the drivers alone are worth much more than that, and the speaker does have some potential - cabinets look decent and building maybe with an outboard crossover, internal wall damping and some good acoustic foam and new T27's and you might have the basis for a decent approximation of a DIY LS3/5a type speaker. At least they have the lineage in the right direction.
I'd be all over these if I'd spotted them in the store if just for the interest and novelty. Nice score and hope you will maybe invest some time into some nice possibilities. I've built a number of DIY version of the LS3/5a and have a number of real LS3/5a's to compare them to. Done right, you can get many of the nice qualities LS3/5a's are known for in a DIY package.
Good Luck!
Regards,
Bart
Moderator, Yahoo! LS3/5a newsgroup (as mentioned above)
LS3/5a enthusiast