Locksmithing/Mosler mosuc4592


Mosler Security Vault Door
Mosler Security Vault  

Mosler Vault
Mosler Vault  

We have a Mosler Security Vault Door in our warehouse that was used back in 70's or 80's by Picattiny Arsenal to manufacture arsenal for the US Army.  The door has been closed since then, and we always wondered what was so important that it has remained closed ever since then.  Our landlord doesn't know the combination.  He didn't know it even existed!!! We have the door blocked with junk since it's just basically used as a wall. I'm guessing it's a mosuc4592 vault door.  I tried to use the 50,25,50 default combination, but that did not work.  Do you have any recommendation?  I would love to use the vault as a storage area, if we can get it opened!!  

Thank you in advance,


I always have to start out with - there is no such thing as a "DEFAULT" combination.   I don't know who started this term but they should be soundly horsewhipped!   All it does is to create confusion about locks.

The majority of safes and doors leaving the Mosler factory (especially the GSA equipment) had the combination set on the 50-25-50.   This was standardized, as the items may sit in warehouses for many years before being used, and it made it simple to figure out a lost combo on a new piece of equipment.   According to the DOD security manual (I'm retire Army), combinations of security equipment is "SUPPOSED" to be reset back to this combination when it is removed from service or placed in storage.   However, the reality is that this rarely happens.

There are ONLY three reasons a safe lock will not open, they are (in order):
1.  Incorrect dialing sequence, (operator errors)
2.  Incorrect combination, (wrong numbers)
3.  Mechanical problems.

I would first recommend that you ensure that you are dialing it correctly.   This is the BIGGEST mistake most people make.  The proper dialing sequence for this lock is:

4 times LEFT to the first number (50)
3 times RIGHT to the second number (25)
2 times LEFT to the third number (50)
1 time RIGHT until the dial stops (should be around 80).

NOTE:   Left is counter clockwise, Right is clockwise.  DO NOT count the revolutions of the dial, count the INDIVIDUAL number as it arrives at the 12 o'clock index mark.   For instance for the first number you will turn the dial counter clockwise (left), stopping the fourth time the number 50 arrives at the index mark - or left to 50 once, 50 twice, 50 three times, stopping on 50 the fourth time.   Use the same method for the next sequences.

If it still won't open, then the numbers probably are not the correct numbers.   As this is most likely an MRK-302/402 lock, it is manipulation resistive, which means that the door and lock will probably have to be drilled.
NOTE:  I never recommend using locksmiths for safe (or vault door) work.  You need a trained safe technician from a local safe company.   In this case they should probably also have GSA equipment training.

GSA containers have very specific requirements for opening and repairing.   If the door IS being used for storage which requires a GSA door, then these rules have to be followed.   If not then the label needs to be removed, if the door is opened and repaired by any other methods.   My recommendation is that it be opened and repaired in an approved manner, as this will maintain its integrity and GSA compliance, which will be beneficial later on if the door is sold.
As these locks have not been made for over 11 years now, it should be opened in a manner that does little to no damage to the lock.   Again, if it is not going to be used for GSA purposes, then it can be retrofitted to use any lock, however the GSA label needs to be removed as it may no longer meet the GSA specifications.

If you don't have a local safe company with a trained safe technician, let me know where  you are located (zipcode) and I'll see who I know and can recommend.


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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 AllExperts.com

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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