Hi. I think you may have the engine and frame numbers the wrong way round, that would make them both correct for a 1953 A10 plunger (the frame number series is actually 'BA7S' and not '5' a common mistake with the often poorly stamped factory numbers. Its a pity that its not a A10SF as you would have something rare and desirable. Regards, Peter. ps. you will have to outbid me on ebay first!