We interrupt European and American video teams keen to capture the Guitar Guru in his natural habitat, surrounded as he is by scores of the weirdest guitars man has even planned to connect with a jack plug and amp. Because it is time once again for the Guru's monthly Making Music column, and Paul Day (as mere mortals do call him) has a job to do. Straight ahead, oh Guru-like being.

Jeff Beer (Pencoed, Mid Glam): "Can you give me some info on a Roger semi-acoustic I bought some years ago for £3? It faintly resembles a Rickenbacker semi, and has two pickups with stars for polepieces, cast floating bridge, chunky seven-piece neck, and tortoiseshell binding on the body. I've asked everyone about it and ended up with a big fat zero. Can you help?"

W J Bonney (Flint, Clwyd): "I have a Burns Marvin guitar, scroll-head type, number 810254. Would you please tell me the date of manufacture, and what happened to the Burns guitar makers? Also, the trem goes out of tune — can I fit a Kahler easily?"

Lawrie Moore (Harrow, London): "I would be interested to learn about my WEM Sapphire 12-string solid electric. It has three pickups (microphonic), and is serial 10037. It cost me 60 quid and is a delight to play."

Mr Gilles (Coventry, W Midlands): "I recently acquired for the sum of £40 a Burns Baby Bison bass (designed by Baldwin). Have you got any info on this gothic monstrosity? How much is it worth?"

Hello, Guru-followers. Let's see. Despite its rather bland appearance, Mr Beer's guitar does have a quite fascinating pedigree. Roger instruments originated from Mittenwald, West Germany, the products of Wenzel Rossmeisl and his son Roger. The guitars were imported into the UK by Boosey & Hawkes in the late 1950s and early 1960s; the majority of the range consisted of high quality, big bodied acoustics and electric-acoustics. However, as a token gesture of acknowledgement to the emerging solid body electric, Roger added Mr Beer's model, the Roger 54.

It wasn't even a real solid-body — the lack of f-holes disguises its hollow interior. The electrics were all mounted on the floating metal control plate which was in a copper hammered finish. The 54 was available in sunburst or natural finish, and retailed at £48 in 1960; probably the best-known user of Roger guitars in the 1960s was Mike Millward of the Fourmost ("Oh yeah, we know him well, Guru" — rest of editorial staff).

Roger Rossmeisl worked for Rickenbacker in the late 1950s, hence the styling similarity to early Rickenbacker semis. After journeying to America Roger Rossmeisl worked for Gibson before Rickenbacker, and then moved to Fender in 1962 where he designed various acoustics culminating in the Fender Montego and Hand Carved Ltd acoustic-electrics in 1970. I've heard reports, as yet unconfirmed, that Roger Rossmeisl died recently, which would mean the sad loss of a talented, individual, and influential craftsman.

Current value of Mr Beer's Roger 54 is hard to determine as very few people know of the Roger brand. All the Roger guitars I've seen for sale languish around the £70 mark — way under their true value, I feel. But the 54 solid isn't sought after and prices can be as low as £10, rising to the heady heights of £40 (these prices based on the four examples that have come my way over the past two years). At £3 Mr Beer's was certainly a bargain!

The Burns Marvin that Mr Bonney owns was made between 1964 and 1965 and is one of the most sought-after of the Burns solids — current value would be around £800, but only if it's in mint, original condition. I stress this because anything you change on or add to the Marvin will drastically reduce its value. The trem system can work better than a Strat's when set up properly, so get someone to look at it rather than putting on the Kahler. Please. Jim Burns was the man who started Burns guitars, and he sold his company to Baldwin in 1965, who carried on until 1970.

Watkins, WEM and Wilson guitars all came from the same maker, allied to Charlie Watkins' WEM company based in southern England (best known for their innovative PA equipment in the 1960s). WEM made guitars from about 1960 until the late 1970s, and the most popular of these were the Watkins Rapier series. The WEM Sapphire range was altogether more upmarket (twice the price, in fact), and Mr Moore's 12-string sold when it was issued in 1965 for £68. I'm not surprised the pickups are microphonic given my experience of other wood-filled Watkins/WEM/Wilson pickups. Current value of the WEM Sapphire 12-string would be about the £60 that Mr Moore paid for his, based on my rule-of-thumb generalisation that obscure electrics are often worth their original retail price.

Gothic monstrosity, indeed! Mr Gilles' Baldwin Baby Bison bass is quite a conservative model by Burns/Baldwin standards. I would estimate his Baby Bison to be circa 1968 — there should be a sticker bearing the date on the underside of the control plate. This model first appeared in 1965, just prior to the Baldwin takeover in September of that year. The original Burns design differed in quite a number of ways and in fact was not officially available in the UK, being for "export only". The true Burns examples are virtually impossible to find — I've never seen or heard of one, in fact. The matching guitar version has proved to be a little easier to unearth, although one bearing the actual Burns logo hasn't been discovered so far. The Baldwin company later revised the styling of both guitar and bass models and yours is one of these, with the characteristic "flattened-scroll" headstock. Production ceased in 1970, and since then all Burns and Baldwin instruments have become increasingly harder to find, especially in good condition. However, examples of the Baldwin Baby Bison bass are still surprisingly common, unlike the guitar version, and a realistic current value is around £125 for an as-new example.