The SC71’s story begins in post-war London, when Ingersoll Security was headquartered in Clerkenwell and later moved to Ruislip. The first version of the lock, then called the RA-71, appeared in British magazines around 1950. The marketing of the time reflected an era focused on craftsmanship and domestic security — and the RA-71 set a new standard for both.

Invented by Jack Taylor & Leonard W Young, renowned lock designers, with the patent originally filed on the 11th of September 1947. The Ingersoll 10-lever mechanism was revolutionary. Taylor’s goal was simple: to produce a lock so well-made and so resistant to tampering that it would stand the test of time. Decades later, his design is still in use, with only minor updates — a remarkable feat in the world of mechanical security.

The SC71’s exterior cylinder is protected by a hardened steel dome, also known as a shroud. Originally produced in polished brass and now also in chrome finishes, this dome is made from high-tensile spring steel, making it almost impervious to drilling or sawing.

Where ordinary cylinders expose the lock body to direct attack, the SC71’s dome absorbs and deflects impact. This anti-drill shield was far ahead of its time and remains one of the defining reasons the SC71 continues to outperform many modern locks.

One of Ingersoll’s most innovative features was its key registration system. For decades, SC71 keys could only be duplicated by Ingersoll themselves, ensuring total control and preventing unauthorised copies. Each key was accompanied by a registration card bearing its unique code.

Although the original patent protection has now expired, the principles remain the same:
Genuine SC71 keys should only be cut using the original code number, not by tracing an existing key. Keys cut incorrectly on substitute blanks can cause premature wear, damage to the cylinder, and compromised security.

Always purchase your replacement keys directly from Ingersoll or authorised locksmiths to preserve the lock’s precision and reliability.

The SC71’s lockcase, or body, houses the mechanism that performs the automatic deadlocking action. When the door closes, a spring-loaded bolt is depressed, causing the main deadbolt to shoot out automatically into the strike plate. Once engaged, the door is securely deadlocked — preventing the classic “credit card” or “slipping” attacks that defeat basic latches.

Key Features of the Lockcase:

• Optional double-locking on SC71 model
• Auto-deadlocks every time the door closes.
• Solid machined internal components for long service life.
• Updated in the 1980s to include a third fixing screw for additional strength.

While the Ingersoll SC71 predates BS 3621 (the British Standard for thief-resistant locks), its security easily rivals or exceeds that of many certified products.

From the outside, users can double-lock the door by turning the key 360° and removing it. When double-locked, the internal handle becomes inoperative, preventing access even if a burglar breaks a nearby window or fishes through a letterbox.

For insurance purposes, most doors with an SC71 should also include a secondary BS 3621 mortice deadlock, ensuring compliance without compromising usability.

A defining advantage of the Ingersoll SC71 lock is its modular, serviceable design.
Unlike most nightlatches that must be replaced entirely when one part fails, the SC71 allows every major component to be purchased and replaced individually:

• Lockcase – the main mechanism housing the bolt.
• Cylinder assembly – containing the 10-lever key system.
• Strike plate (keep) – available for both inward- and outward-opening doors.
• Fitting kits and extensions – to adapt the lock to various door thicknesses.

This modularity means the lock can last for decades — even generations. Locksmiths can easily renew worn parts without disturbing the door, and homeowners enjoy a lock that remains serviceable long after installation.

Few locks in production today can boast the same level of sustainability and longevity, making the SC71 not just a lock but an investment in lasting home security.

This customer receipt from September 1954 gives you a glimpse of the continued support we provide to Ingersoll customers.

The Ingersoll SC71 lock isn’t merely a piece of hardware — it’s an enduring example of British engineering excellence.
With its 10-lever precision cylinder, hardened dome protection, reinforced strike plate, double-locking mechanism, and modular design,
the SC71 remains one of the most secure and serviceable nightlatches ever made.
From 1950s advertisements in Punch magazine to modern-day installations across the UK, its reputation has never wavered.
If you value true mechanical security — not just a badge or buzzword — the Ingersoll SC71 lock remains the gold standard.