ID of Merlin blocks
 

I have two Merlin II used tall deck blocks from an engine purchase gone bad. World Products told me on the phone that they do not S/N these blocks. Today I got a chance to examine them and I found stamped on the bump out under the fuel pump pad, on the same plane as the pan rail the following. Both blocks had 81111 stamped closest to the rail with 2182 and 2192 stamped under the 81111 on the different blocks. Does any one know if this is a S/N or perhaps these are a builders job #. Any helpful information would be appreciated.