As the insides of the Beeb were updated over its lifespan, so too was its outward appearance. The first Beebs had a "BBC microcomputer" legend on the function key strip. Later this was changed to the longer "British Broadcasting Corporation Microcomputer System" wording. There is at least one book which shows a Beeb marked "BBC computer" but I think this is just a bit of artistic licence rather than a rare variety!
The case itself was revised over the years with "rough" and "smooth" versions appearing. Later lids also had a "rib" running along the back to partly cover up the ventilation slots.
Some early Beebs have a bit of fabric stuck underneath where the speaker is located.
The keyboard itself went through a few changes. Most keyboards seem to be made on white board with keytops similar to the Master 128 but some are a purple colour with more pointed keytops. Even with the most common Master-type keytops, there are variations in letter spacing on the SHIFT, COPY and TAB keys. There is also a "wide" and "narrow" variety of the "R" key if you look closely enough.
I think the very first Beebs had the serial ROM socket hole completely exposed. Later, this was covered over with a perforated panel which could be removed if the speech upgrade was fitted but there are some Beebs with no perforated panel.
The speaker is variously provided with or without a protective grille on some Beebs.
Underneath, you will notice slight differences to the writing, most particularly to the capacity of the power supply as this changed over time.
At the very back, there are lots of differences and I have discovered four varieties so far:
This is a very early type sporting the original full length ventilation slot and early copyright wording. The two FIX positions are also marked, as is the Reset hole which is cut out in the case.
Although not widely known, the BBC micro could be modified to disable the BREAK key and replace it with a reset switch at the back. This modification is detailed in the BBC Service Manual and the contact points for the reset switch are present on all the versions of the motherboard but its inclusion on the back of the casing seemed to be soon removed.
Soon after, the patent was still pending but the credit for Allen Boothroyd was removed. The analogue socket hole was widened slightly, presumably to reveal the screw holes, the use for which those of us still using serial and parallel ports know and detest only too well!
The video out BNC connector would normally be present. I just happen to have removed it from this particular Beeb.
Almost the same as the previous version but the patent is no longer pending and the directional arrows have gone.
No mention of the BBC Micro here - were Acorn beginning to disown Auntie even back then? Let's not forget that none of the BBC Domesday documentation gives credit to Acorn anywhere and I have seen the BBC Master described in some later Acorn publications as the "Acorn Master 128"!!
At no point during any of these varieties is "Econet" recognised as an Acorn trademark (which it is) nor is it given a capital letter (which it deserves)!
Now I come to think of it, I am sure I have seen another variety with "RF Out" instead of "UHF Out". Surely somebody out there will let me know.....