I've recently acquired a Morton M5 Radial engine. It is not complete as it's missing a few parts like a couple of push rods and a couple of rocker arms but the engine is all together and turns over smoothly,but I'm interested to know if you know the specific age or date of manufacture of the engine I now own.The case is stamped with A557 and from what I can gather this engine was assembled andrun by the factory. Other engines that were produced and sent out as kits did not include the letter A.Thank you for any information you might have.