Martin, I can't see what model of bike it is, but there are essentially two versions of the A10, namely the early Rigid and Plunger Frame type and the later Swinging Arm Frame. Sidecar gearing is lower, so a quick check of the rear sprocket teeth will tell you if it is set up as combo, 49 teeth is usual when hauling a sidecar. Solo is 42 teeth.
More important to you is the worry of the frame, so the usual visual check is that the wheels are in line, if it looks straight it probably is. Even so, its a complete bike, bar a few easily found bits, and a runner. If it has papers, even better. Get the tank off, and site the top tube by eye, feel for bends, bows, kinks. If it turns out not so good, its decision time based on the amount of hassle you are prepared to take.
Straightening frames these days is relatively easy, the plunger frame comes apart in two pieces. Here the top tube bows sometimes, or kinks just behind the steering head lug if the bike has been shunted. The later frame is a one piece welded construction, the headstock slightly better braced and repairs are even easier.
Decide if its for you and strike a deal. Value it on what it's worth to you, today. Without pictures or a detailed description giving a value here is hit and miss, better to compare with other bikes on sale and decide how it stacks up.
Swarfy