SYNCOPE is the Laundry codename for a periodic "sweeping" operation that's intended to identify potentially dangerous occultists. From time to time, Laundry officers offer selected occult texts and materials for sale through various outlets, and see what fish rise to the bait. If the Officer In Charge feels that “the fish” warrants further attention, the Office of Surveillance Management arranges exciting evenings of tailing, bugging, and breaking & entering, with further actions (up to Involuntary Induction) available as needed.
The Laundry also conducts SYNCOPE actions abroad, both with and without the cooperation of the host nations. It's a classic "sting" operation used by security services the world over, although they're usually dangling illegal weapons in front of potential suspects rather than cryptic texts in Aramaic and crowns made from human jaw-bones.
Following an embarrassing misstep some years ago, all materials on offer by SYNCOPE are skilled forgeries, or have at least been reliably de-fanged.