how to identfy a No. 1 sear from a No.4 sear.

[Maxwell Smart]

Sears for No 4 and 5 rifles are flat sided - have the same width right through on both arms of the sear, and have flats milled on both faces of the long arm of the sear.

SMLE sears have a stepped increase in width towards the extreme ends of both arms, and do not have the flats on top and bottom faces of the long arm.

Thickness across sear at pivot point - No 4 .248"
- SMLE .218"