Have you ever looked at the bottom of an old LEGO brick and spotted the mysterious letters "Pat Pend"? Then you're holding a special piece of LEGO history in your hands! In this blog post, you'll discover exactly what Pat Pend means, how old these bricks are and what they are really worth.
Pat Pend: An Old Secret Revealed
Pat Pend is simply short for "Patent Pending" - meaning LEGO had invented something revolutionary and applied for patent protection, but was still waiting for official approval.
LEGO printed these letters on its bricks from 1958 until approximately 1974. The patent itself was granted in 1962, but many moulds kept the text until they were replaced.
Why Was This Patent So Important?
In January 1958, LEGO faced a critical problem: their bricks fell apart too easily, and customers weren't satisfied. German retailers especially complained about how unstable the constructions were.
Godtfred Kirk Christiansen (son of LEGO's founder) then developed a brilliant solution: adding small tubes to the underside of each brick. This innovation made the studs of one brick fit perfectly between the tubes of another, creating the famous "clutch power" we know today - strong enough to hold, but easy enough to separate.
LEGO filed the patent on January 28, 1958, though it wasn't officially approved until 1962. However, LEGO continued printing "Pat Pend" on bricks until all old molds were exhausted around 1974.
How to Recognize Pat Pend LEGO
The beauty of vintage LEGO is you can easily identify which era a brick comes from. Pat Pend bricks have several distinctive features:
- The Text Itself
The most obvious identifier is the "Pat Pend" or full "Patent Pending" text printed on the bottom or inside of the brick. - The Small Sprue Mark
All Pat Pend bricks feature a small protrusion on one side - a tiny bump where the brick was attached to the mold during manufacturing. Later production methods eliminated this mark. - The Logo
The earliest Pat Pend bricks (until approximately 1963) display the original LEGO logo, which later evolved into the modern design we recognize today. - The Plastic
The very first Pat Pend bricks were manufactured from Cellulose Acetate, a plastic that warps over time. From 1963 onwards, LEGO switched to ABS plastic, which remains the standard today.
Pat Pend Obscured
There's also "Pat Pend Obscured" - bricks where the text was removed from the mold, leaving only a faint mark or bumpy area. This occurred during the transition period after patent approval, when LEGO still utilized existing molds.
Are Pat Pend Bricks Valuable?
The honest answer: usually not on their own. LEGO made Pat Pend bricks in huge numbers for more than fifteen years, so a loose 2x4 in a common colour is an everyday find for its age and sells for little. The value sits elsewhere:
- Complete Early Sets
Boxed sets from the late 1950s and 1960s, ideally with the original box and instructions, are what collectors pay real money for. - The Earliest Bricks
Cellulose acetate bricks from before 1963 are the oldest Pat Pend bricks. Warping and discolouration are common, so condition matters a lot. - Moulding Errors
Bricks with misprints or misaligned moulds are genuinely unusual and can sell for far more than a standard brick. - They Tell LEGO's Story
These bricks document LEGO's evolution from a small toy company to the global brand it is today. They mark the pivotal moment when LEGO invented the iconic building system still used worldwide.
The Timeline of LEGO Patent History
Here are the key milestones:
- 1949-1958: First plastic LEGO bricks, without the tube system
- 1958-1962: Pat Pend period begins - patent filed but awaiting approval
- 1962-1974: Patent officially granted, but "Pat Pend" marking continues
- 1974-1979: Transition years mixing old and new production
- 1980-present: Modern LEGO without Pat Pend markings
Tips for Authenticating Your Vintage LEGO
Wondering if you have Pat Pend bricks in your collection? Here's what to check:
- Turn the brick over and examine the underside for "Pat Pend" text.
- Look for the small sprue mark on the brick's side.
- Verify the logo style - old versus modern LEGO branding.
- Test the plastic - does it feel brittle or show warping? This indicates very early production.
- Inspect the tubes - early versions have different tube configurations.
Important note: Not every vintage brick displays "Pat Pend" - some parts were too small for the text. Absence of marking doesn't automatically indicate a newer brick.
More Than Just Letters
"Pat Pend" represents far more than two mysterious words on old bricks. These markings commemorate a revolutionary moment in toy history - the foundation for billions of creations built by children and adults worldwide.
Next time you encounter vintage LEGO, take a moment to examine the underside. You might just be holding a piece of history!
Found an old LEGO train among your vintage bricks? Our guide to vintage LEGO trains helps you tell 4.5V, 12V and 9V apart.
