Numbers on Engine

[MattM]

My "T" is registered as a '24 most likely due to the rear of the head has being stamped 3 24. However, the engine number seems to fall with in May of 1925. My question is to the left of the water inlet is stamped "M1", does anyone know what this means?

[Wayne Sheldon]

It is generally believed that those numbers and/or letters on the block, and some of the letters and numbers found on heads also, were mold and pattern identification numbers. They were used in the factory for quality control. Molds were used to cast blocks, patterns were used to form molds. Both were used many times over until they began to wear out. If quality control found defective castings before or during machining and assembly, they would use the numbers and letters to trace back to the molds and patterns to check for wear or other damage.
I have never heard of any records of any value for those numbers, and they serve no real purpose today.

[MattM]

Thank you Wayne!