I have the Sv500 Speed Vault. The combo you set is not numeric, but a set of "entries". An entry is one or more keys pressed at once. Minimum is 3 entries for a combo, and max is 6. With 6 entries, some using more than one key at once, you can set it complicated enough for the kids to never guess it.
I've had the battery die once since I bought it. I think it took about a year. Just open it once a week or more to test the battery. If the battery dies, you must use the key to open the door to access the battery compartment.
When' the door opens, the counter weight makes a loud clunk sound. If you are trying not to alert someone, then wait until you have to open it, and it only takes 2 seconds from combo entered to gun in hand.
If you leave the house empty, recommend placing the gun in a real safe. This safe is only for quick access and safety around kids, not anti-theft. It will keep visitors and other "honest people" from getting to the gun, but not a real thief.
There is a nice bright LED bulb to help you get your hand on the grip properly. The muzzle is stuck in foam rubber, so the grip is presented to you for quick retrieving.
For the money, it's hard to beat the features. I chose the keypad version over the biometric for two reasons. 1. Biometrics can be difficult to make work every time. The reader is sometimes unable to scan the print without several tries. Not ideal for this application. 2. I like the idea of being able to give the combo to my family as required. I don't need to program in several fingerprints. The situation may also arise where I might need to give the combo to someone in danger over text message or phone call. Can't do that with a print reader.
That's all I have. If you have questions, feel free.