OAC (204) was similar to 203, being built at the same time, though at Filton rather than Toulouse.
OAC, and presumably 203 too, had slight differences in wing spar construction from the later aircraft.
OAG and OAF (214, 216) were also lighter than the rest.
Today, the prototypes would not be called that, 'Technology Demonstrators' would be more apt, as they were very different to the production models.
In length (9 feet shorter), visor system (the original solid visor and 'peepholes' would have never been certified for pax service, but Marshalls of Cambridge were developing a tinted glass, heat resistant visor as fitted to the pre-production aircraft onwards), the nose originally went down to 17 deg, reduced to 12.5 deg on production aircraft.
The prototype's engines were far less developed that the OL593 mk.610's fitted to production models). Production engines were much less smoky as well as more powerful.
The prototype's nozzle/thrust reverse system differed too, the familiar 'buckets' being from pre-production aircraft onwards.
An analogue intake control system was fitted originally (and found to be insufficient), the digital system first flew on the UK Pre-Production aircraft in 1973, three years after the decision to take advantage of new computer technology for the digital system. The original system used local sensing of air data, the production system used mainline A/C manometric pressures, being synthesized to the correct local pressures by the digital computers.
Cockpit layout was different too (space for a moving map display on the prototypes-the French really thought overland supercruise would be allowed for a long time), many instruments in the flight deck differed on production models too, the wing was different on the prototypes being refined further for later aircraft from the original planform, they also lacked the tailcone extension fitted from the pre-production aircraft onwards.
Those are just a few that come to mind, really the first two prototypes were different aircraft almost.
The pre-production models were what we today would call 'prototypes', sometimes we could rob components from the pre-production UK aircraft, preserved at Duxford since 1976, we did not do the same with the UK prototype at Yeovilton.
But even 201 and 202, the first two production aircraft that never entered service, were not fully up to airline standard.
After the production models entered service, a range of improvements were included;
Structural weight raised to 408000lb
Further aft C of G cleared for take off.
Improved fuel loading.
Max subsonic cruise Mach number raised to M 0.95
Sharper fin leading edge.
Extended control surfaces.
Thinned and lowered engine intake lip.
In service, the aircraft certainly showed how they were virtually hand built, take a panel off one and it would not always fit on another.
Individual aircraft had minor defects that would show up from time to time, with often long periods in between, the 2001 tank mods were hard at first, EADS had measured a French aircraft, hardly any fitted OAF, so each liner had to be made not only for a specific position, but also a specific aircraft.
OAG was laid up in the early 80's, then returned to service in 1984/5, as parts had been extensively robbed from it the return to flight was really a rebuild.
OAG, right to the end, had slightly different cabin emergency lights and other similar items, and spotters tell me you could always tell if a Concorde was OAG, as the radio transmissions appeared to be louder and clearer.
OAD was generally the most reliable aircraft in the BA
fleet, though towards the end it burned the most fuel, (OAF and OAG were better in that respects, specially OAG towards the end).
No surprise that OAD did the last round the world charter in late 1999, then in early 2000, the 'African Queen' charter, it also seemed always to be allocated for crew training at Shannon and Chateauroux too, at least in the last few years.
If we had been allowed to bring either OAA or OAB up to flight condition in the past two years, most would have preferred OAA.
Concorde always had a degree of fuel/hyd seepage due to the expansion at Mach 2, when OAE was delivered to BA
from BAC Filton in 1977, it was worse for this than the others.
But in they all went through phases of requiring work in this area, in 1997 OAE was the worst for this, in 1998 OAB, in 1999 OAG.
OAF gave us quite a few headaches in this area over this period too.
However, after the tank mods, this problem was less apparent, not the physical presence of the tank liners, as only 5 and 8 tanks were fully lined, but maybe EADS had the sealants that we'd been urging BA
to provide us with for years! Also the amount of preparation done to the tanks prior to refilling them must have helped.
The severity of these seepages was decided by the position and drops per minute of any leak, triggering an input to rectify them, a seepage in front of an intake for example would need work to fix it quicker than many others, but of course the authorities and manufacturers set the criteria in this.