BS EN 4124:2018 Aerospace series. Shank nuts, self-locking, in heat resisting nickel base alloy NI-PH1302 (Waspaloy), silver plated on thread, for 60$0D swage. Classification: 1 210 MPa (at ambient temperature) / 730 $0DC

Dimensional tolerances
Designations
Fasteners
Threads
Marking
Nickel alloys
Coatings
Dimensions
Surface treatment
Locknuts
Silver
Heat-resistant materials
Metal coatings
Nuts
Aircraft components
Threaded fasteners
Internal-thread fasteners

Link: BS EN 4124:2018 Aerospace series. Shank nuts, self-locking, in heat resisting nickel base alloy NI-PH1302 (Waspaloy), silver plated on thread, for 60{$permalink}D swage. Classification: 1 210 MPa (at ambient temperature) / 730 {$permalink}DC
Source: BSI Standards