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The lock is functionally identical to the ASSA Twin 1800 and the design seems to be based from it, with the patents for both sharing an inventor (Bo Widén), however unlike many of the other ASSA Twin locks, the Lockwood Twin uses only 3 pins in the sidebar. The Lockwood Twin is part of the Twin series of locks that use pin-tumblers and a sidebar to provide two layers of security.
The Twin is also is similar in function to the Schlage Primus cylinder.
Principles of operation
The Lockwood Twin uses up to six pin-tumblers and 3 sidebar finger pins. Each of the driver pins in the pin tumblers can be equipped with security pins, (however in practice this is not always done) and functions in much the same way as any other pin-tumbler locks. The sidebar finger pins must be raised to the correct height by the key, with each key system having the same sidebar height, shared across all locks and keys.
Key Markings and Meanings
The sholder of the key contains the Key Profile (Generally starting with T) used in that system. The same marking is usually stamped on the plug of the lock on the right hand side. Keys with a key profile that do not match the plug will generally not fit that plug.
The first line of text stamped on the key (from the top of the key) is System Number EG DDHA059 and denotes for which system it is, ie, a master key and an operational key for the same system will both have the same system number.
The second line of the key contains the key number (Ie A1, MK) and the issue number (Ie 0001 for the first key issued)
The Twin is disassembled in the same way as a traditional pin-tumbler cylinder. The sidebar does not cause too many problems when the plug is removed. When the key is removed from the exposed plug the finger pins will be forced out by spring pressure.
- Remove the cam or C-clip.
- Insert the key and turn the plug 45-90 degrees.
- Withdraw the plug from the cylinder. (A plug follower is recommended)
- Remove the chamber casings and take out each pin-stack individually
- Remove the cam or C-clip.
- Withdraw the plug from the cylinder.
The Lockwood Twin system may be vulnerable to one or more of the following:
The Lockwood Twin can be picked in much the same way as any other lock of it's style. The conventional pins (The 6 pin-tumblers) pick with relative ease, especially considering the excessive master keying usually applied to these systems. When the conventional pins have been picked the lock turns about 1/8th turn, and the sidebar pins must then be picked, which is generally fairly straightforward given an idea of what the key looks like, and if no success is had it's possible to rotate the plug back just enough to reset the sidebar pins, but not the top pins.