Great Britain Qv 2½d 1883 Sg139 Inv Wmk - Value?

Any advice on my recent find would be much appreciated.

The anchor watermark is inverted and he SG Concise has it listed used at £180, in reality though what do you guys think.:

Well, if I were estimating it in the US, I'd guess if Scott were to list it they'd list it at $180, since they seem to follow SG pretty closely, other than doing any actual dollars to pounds conversion. :)

Two sides cut into is Avg centering, three points of fault. Perfs look good, I don't see evidence of tears, thins or creases, so I'd call it at three points total.

$180->90->45->22.50

Sp street value $22.50. If there are hidden faults, drop accordingly.

Thanks for the great advice, it really is much appreciated by this newbie.