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Locksmithing/combination change key for 1966 Mosler model 12


Mosler model 12
Mosler model 12  
QUESTION: Hello, I'm considering buying an older Mosler, single-door safe (~300lbs.) for general home use.  I'm have some informal familiarity with changing combinations on older S&G-type mechanical locks, and wondering how to find the appropriate combination change key for this safe.  As you can see on the attached image, there is a UL 'relocating device' number: 847658, but I'm not sure this means what I think it means.  

I'm aware that older safes like this have inherent limitations, but I've had a lot of electronic locking systems fail (XO-7, XO-9, etc.) on me over the years, and I specifically want to find a mechanical lock.  Thanks in advance for any help.



Couple problems - first as Mosler has been out of business since 2001, specific parts and tools like change keys are NOT readily available, though there are some aftermarket sources for some change keys.    Second the photo of the back cover and the labels doesn't have anything to do with the lock installed on your safe.

As the SMNA label indicates that your safe is basically a fire resistive safe, the lock may be a hand change lock.    The UL "relocking device" label has nothing to do with what you are requesting, however "IF" you elect to disassemble the lock, you WILL activate the relocking device, and IF you don't reassemble it correctly, the first time you close and lock the door may be the last time you get it open.

Generally I DO NOT recommend lock disassembly as a DIY project, for the same reason that I don't recommend using locksmiths for safe work.   Lack of training, knowledge and tools can cause extremely expensive lockouts.  

If you actually need a change key, the first step is to ID the lock that is installed on your safe so that we can look into finding a change key for it.    If one is still available, I don't have any problem selling you one, however I have a hold harmless form that we require your signing, as we have no control over your use of, or misuse of the tool or instructions.   We also are not going to provide training.

Generally my first recommendation would be to have the lock correctly serviced and the combination reset by a safe technician from a local safe company.

So the next step would be for you to remove the round cover (in your photo) to reveal the lock underneath, and provide a photo of the lock.

---------- FOLLOW-UP ----------

Mosler lock face
Mosler lock face  
QUESTION: Excellent, and thank you. Does the attached photo of the lock face help?

Hi Tim,

That is the photo that I needed to see!   This is a hand change lock - change key won't help you here.

The lock has to be disassembled and a new combination set on each wheel manually.

As I mentioned earlier, I NEVER recommend lock disassembly as a DIY project.    Fortunately there is no external relock device directly attached to the lock to worry about, however this lock does have an internal relocking trigger which can cause you lots of problems if everything isn't reinstalled correctly.

My recommendation for this one - especially considering the cost to have the safe opened if you accidently lock it up, would be to have the combination changed by a trained safe technician from a local safe company.

If you decided to make it a DIY project DO NOT close and lock the door until you have successfully locked and unlocked the door - in the open position.

If you don't have a local safe company, let me know where you are located (zip code) and I'll see who I might know and/or recommend in your area.  


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Terry V. Andreasen (Andy)


Safe and Vault related Questions; Antique Safe Repair and Restoration; With over 42 years in the Safe & Vault industry, if I can't answer your question I know where to get the answer. Current Project: Restoration of an Ely Norris Cannonball Safe from the early 1900's. Will answer Safe & Vault related questions concerning age, value, restoration, moving, opening & repairing, parts, operation and history. Note: It is not my intention to teach you to open safes or to provide information which may aid in the unlawful opening of a safe. I will not give out drill points or information which I deem inappropriate.


44 years in the Safe & Vault Industry. Owner and Service Manager for one of the largest Safe & Vault companies on the West Coast. Graduate of Lockmasters Safe Lock Servicing, Safe lock Manipulation and Safe Deposit Lock Courses. Graduate of Locksmith Institute. Certified Instructor for the California Locksmith Association teaching Basic and Advanced Lock Servicing, Basic Safe opening and Repairing. Factory Trained by AMSEC, LORD Safes, LeFebure, Mosler, KabaMas, LaGard and Sargent & Greenleaf Author of "The Coffee Table Guide to Antique Safes".

SafeCrackers International and the National Antique Safe Association Safe & Vault Technicians Association (SAVTA)

The Coffee Table Guide to Antique Safes

Graduate of Locksmith Institute 1972 Graduate Lockmasters Safe Lock Servicing 1974 Graduate Lockmasters Safe Lock Manipulation 1975 Graduate Lockmasters Safe Deposit Lock Servicing 1985 Instructor Certified - California Locksmith Association - 1985 Factory trained by AMSEC, MAJOR, STAR, Johnson-Pacific, Kaba-MAS, Allied-Gary, ISM, Lord, Brown Safe, EXL, Mosler, Diebold.

Awards and Honors
2009 - 2015 - Listed in AllExperts Top 50 Experts. All Expert Categories - Safes & Security Containers, Locksmithing, Antique Safes. Retired US Army Chief Warrant Officer (CW4), with 39 years of total service. With numerous awards from Vietnam, Desert Storm and Operation Iraqi Freedom. US Navy - 1971-1981 US Army Reserve 1984-2013 US Army Retired

Past/Present Clients
US Secret Service, FBI, BATF, Local Law enforcment agencies, Diebold, Hamilton Pacific, Red Hawk Int., Chubb International, Bank of America, Wells Fargo Bank, Mechanics Bank, El Dorado Savings Bank, many Credit unions and smaller banks. McDonalds, Togos, BurgerKing, TacoBell, Carls Jr. FoodMaxx, SaveMart, Lucky's, Albertson's, Raley's, Safeway, NobHill, Bell Markets, PW Markets. Great America, Century Theatres, Cinemark Theatres, UA Cinemas, and many homeowners and small businesses. Provide warranty service for lock and safe manufactures. Service Area is Northern California (Fresno to Oregon and Western Nevada)

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