This past year I sold 6 brand new RC72-36 mmm built for L3600 tractors. Part of a deal made with my local dealer
As part of the mower installation, the drain style plug was to be removed and replaced with an Allen head plug thus eliminating the drain. The drain style plug interfered with the mower mounting hardware/
The manuals I had only dealt with the hardware installation. I do not know if there was a mower Owners Manual which recommended removing the socket plug periodically to get rid of any water or oil accumulation
Dave