Looking at the above pictures I posted, you'll see the T that is cast on the inside of the block.
My pad where the serial code is stamped has F54N stamped on it.
I wonder what the G1 stands for that is above the T ??
Ok, I missed that those were your pictures...
In that case you could have a Tonawanda block with a Flint serial number because you have a replacement block. The date code on that block is L 14 6 which tell me it was cast on Dec 14, 1956.