See Scan for perfs. 

BW lists all WA OS stamps with a premium and considerable premium in some instances.

Unfortunately, BW only lists issues from federation, ie 1901. Stamps issued before that are not listed even though they were still in use at federation and beyond.

SG does not list OS for WA or Victorian stamps.

Western Australian OS stamps are popular along with the WA punctured stamps.

A hard stamp to find to complete your OS collection.

i am listing it as line 12.4 however I believe it is compound although compound is not listed in SG or BW for this item. If perfs have been altered then min CV is $200 for line 11. Either way, it is a hard stamp to find OS.

Previous owner listed it in their collection as W41b and it is the closest fit.

I am listing it at 1/4 of catalogue value and less than half CV of cheapest possible OS so you can't go wrong

REGISTERED purple cancellation is also rare and could be a bonus for you.