The stamp photo needs improvement

, I think, to see it clearly... but it is a Glasgow postmark dated August 22nd 1907 which makes it a SG 230 (Scott#131) first issued in 1902 by De La Rue printers.
I cannot see the perfin clearly but it does look like one that might have a letter and a number.
From the photo, I would suggest the hand writing looks to be 8/6 which might refer to UK currency at that time.. 8 shilling and sixpence. That might indicate the stamp was on an envelope later used for scribbled notes as that was common in solicitor's or business offices. The stamp was later removed obviously.