Mills Slot Machine Keys



So you’ve bought a vintage Mills slot machine, got it home, and realized the seller didn't hand over the keys. It’s a classic scenario that drives new collectors up the wall. Without that small piece of metal, you’re locked out of the coin mechanism, the hopper, and the back door—which means you can’t access your winnings or perform basic maintenance. Finding the right replacement isn't as simple as walking into a hardware store; these aren't standard cuts. Let's break down how to identify what you need and how to get your machine open without damaging a piece of gambling history.

Why Mills Slot Machine Keys Are Hard to Replace

Mills Novelty Company dominated the slot machine market from the early 1900s through the 1950s, producing iconic models like the Black Cherry, Bursting Cherry, and Golden Nugget. Because production spanned decades, there wasn't a single universal key. Different locks were used for the front mechanism (often called the 'belly door'), the cash box, and the back door. Over the years, keys get lost, locks get changed by previous owners, and original factory key codes fade from the lock face. If you own a Mills Hi-Top or a mechanical console model, you are likely dealing with a specialized flat key or a double-sided cut that modern locksmiths rarely stock.

Understanding Lock Types and Key Blanks

Most Mills machines use one of a few common lock styles, but identifying them requires a keen eye. The front door lock is usually a tubular or flat slider lock, while the back door often uses a different keyed mechanism to prevent unauthorized access to the internal wiring and hopper. If you are looking for replacements, you will encounter terms like 'P-36', 'P-41', or generic 'Mills replacement keys'. However, buying a generic key online is a gamble. If the lock has been replaced in the last 70 years, a factory-original key blank won't work. You need to inspect the lock face for a code—often stamped near the keyhole—before ordering anything.

Identifying Your Key Code

Before you start spending money on key blanks that might not fit, grab a flashlight and examine the lock cylinder. Many original Mills locks have a code stamped directly onto the faceplate or the edge of the lock body. Common prefixes include numbers like 520, 526, or specific letter combinations. If the code is visible, your job is easy: you can order a pre-cut key to match that code from specialized antique slot machine parts suppliers. If the code is missing or worn away, you will likely need to remove the lock to have a locksmith impression a new key, a process that involves manipulating a blank key inside the lock to create the necessary cuts.

What to Do If the Lock is Seized

Old machines often sit in garages or basements for years, and the lock mechanisms can gum up with old grease and grime. Forcing a key is the fastest way to snap it off inside the cylinder. Instead, apply a penetrating oil like PB Blaster or WD-40 specifically into the keyway. Let it sit for at least an hour. Gently insert the key (if you have a broken one or a near-match) and work it back and forth without applying heavy rotational force. The goal is to loosen the pins or wafers inside. If the lock is completely stuck and you have no key, drilling the lock should be a last resort, as it destroys the original hardware and reduces the machine's value.

Buying Replacement Keys vs. Replacing the Lock

If you cannot find a code and cannot impression a key, you face a choice: replace the lock entirely or drill it out. For serious collectors, maintaining originality is paramount. Original Mills locks are cast iron or steel with specific stampings that match the era of the machine. Swapping them for a modern cam lock looks wrong and degrades the authenticity. It is almost always worth paying a specialist to craft a key for the original lock. However, if the lock is already damaged or replaced with a non-authentic part, swapping it for a modern, functional lock is a practical solution to secure your machine.

Key/Part Type	Best For	Difficulty	Estimated Cost
Code-Cut Replacement Key	Visible lock codes (e.g., P-36)	Easy	$15 - $30
Generic Mills Key Set	Unknown code, trial and error	Medium	$20 - $50
Locksmith Impressioning	Missing code, lock intact	Hard	$50 - $100+
Full Lock Replacement	Damaged or non-original locks	Medium	$40 - $80 (plus labor)

Maintenance After You Get In

Once you finally get that Mills slot machine open, don't just close it up and forget about it. The lock mechanism itself needs care. Use a graphite lock lubricant rather than oil to keep the tumblers moving freely—oil attracts dust and eventually creates a sludge that jams the key. Check the lock mounting screws; vibrations from the machine's payout mechanism can loosen them over time. If you have multiple keys made, store a spare somewhere safe and dry. These keys are often made of soft brass or steel that can bend or break if twisted too hard in a stiff lock.

Security for Your Collection

While these are mechanical antiques, they can still hold significant amounts of cash if you use them as piggy banks or for home gambling nights. Never leave the key in the lock. It sounds obvious, but it's a common mistake. If you have children or guests, consider a secondary security measure, like a cover over the coin tray or keeping the machine in a locked room. Original Mills keys are surprisingly effective picks for other machines of the same era, so treat your keys with the same security you would apply to modern iGaming account credentials.

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