It does go back to well before NDT
"The Worshipful Company of Gunmakers was incorporated by Royal Charter in 1637 to promote and regulate gunmaking, a role it still fulfils today".
"It is still done as it has been since the Company was established in 1637: by firing the gun with an over-pressure charge of powder. If the gun survives undamaged, it will be safe to shoot. If it doesn’t, it is deemed unfit for sale "