Normally I get excited when I see old motorbikes in barn find condition but, unfortunately, not with the Armstrong. If you want to buy one cheap for spares then these are probably ok.
However, if you want to buy one to restore to some level of running condition then this can be a problem unless you've closely examined the one you going to bid for and you know precisely what needs doing to it. At the end of the day, a good runner, ready for the road, can cost you less than £1000, whereas, it can cost a good part of this amount to get a barn find condition one up and running again providing its not completely knackered.
A HD MT350 is always a better bet because they are worth a lot more than the Armstrong in good running order. I have one of each and I think they are marvellous bikes but not worth that much even in beautifully restored condition.