BS EN 4122:2018 Aerospace series. Shank nuts, self-locking, in heat resisting steel FE-PA2601 (A286), silver plated on thread. Classification: 1 100 MPa (at ambient temperature) / 650 $0DC

Silver
Dimensions
Nuts
Fasteners
Marking
Heat-resistant materials
Metal coatings
Aircraft components
Locknuts
Threaded fasteners
Surface treatment
Steels
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Link: BS EN 4122:2018 Aerospace series. Shank nuts, self-locking, in heat resisting steel FE-PA2601 (A286), silver plated on thread. Classification: 1 100 MPa (at ambient temperature) / 650 {$permalink}DC
Source: BSI Standards