According to Donald Dallas in his "The British Sporting Gun and Rifle", both Purdey and Scott could license the combined patents: "Purdeys quickly realised the superiority of the Scott top lever allied to their bolt and made a reciprocal licensing agreement with Scotts; Purdey could use the Scott lever in conjunction with their bolt and Scotts could use the Purdey bolt along with their lever. In addition Purdeys could license the dual patent to the London gunmakers and Scotts to Birmingham and the regions. Such licences were not cheap, Purdey charged the London gunmakers $2 per gun for the right to use the Purdey bolt and Scott top lever. Provided patent fees are paid, a patent can run its full course of fourteen years. The Purdey archives show virtually every single London gunmaker being licensed to use the bolt, and considering the £2 royalty fee per gun, a not inconsiderable sum in the 1860s, Purdeys must have netted a small fortune until the patent expired in 1877. No doubt Scotts accrued the same benefits." So maybe not out of the realm of possibility for the PUN to refer to the dual Purdey/Scott patent, as licensed by Scott.
Sorry to lift a whole paragraph from Mr. Dallas, but he explained more succinctly than I could have.
