NT6541 STEEL NUT.  Right hand thread Nuffield Steering Box Nut. 

For Nuffield tractors from serial number 5128 onwards.

Also available in Bronze, see part number NT6541B

For more details view item 25 in this parts book drawing of the 
Nuffield tractor Steering Column.

Fitted to:

• Nuffield Universal Three (3DL), Universal Four (4DM)
• Nuffield 342 – 460, 10/42 – 10/60