Question about this, Sykes Fairbarn or letter opener?

[kersten]

Hey fellow collectors - I picked this up years ago - like 20 years ago - is it a cheap copy or is it a real Sykes FB dagger? I am thinking it's just a letter opener - it has some markings on it. If it's worth anything I will sell it on eStand.

[kersten]

another photo

[nickn]

Post war commercial made by nowill I think
Probably from the 70's
£20-30

[kersten]

Ok thank you