One of your photos has a chain around the handles ... So it stood for years unlocked and then someone came and turned the dial?
I don't have much information about the Diebold Kienzles. There is probably a 4-wheel "Peerless" lock inside about which I also don't know much. There seem to be Peerless locks with a normal mechanism, which can probably be manipulated. And there seem to be Peerless locks with additional mechanics, probably with the purpose to prevent some sort manipulation, but apparently it doesn't stop the current manipulation methods. Your safe doesn't look like a high-security safe, so it is probably the normal version of the Peerless inside.
I see three options for you.
1) You could learn manipulation of safe locks and manipulate the safe open. This will take quite a bit of time. It will be worth this time only if you have fun doing it.
2) You want to save money and don't care about the safe. Then break it open.
3) You want to keep the safe, but don't want to invest time. Then book a safe tech to open the safe for you. There is the safe tech organization with a list of techs:
http://www.savta.org/savta_tech.php They do have probably an acceptable minimum level of skills. Typically he will make one small hole. A few will manipulate, but probably not with a 4-wheel lock. With standard locksmiths the risk is high, that the result is the same as when you break it open yourself.
