So I have to mark this as "Not A Bug" even though it is.
For WHATEVER reason UO in their ultimate wisdom only applied the big gump to what would be the "silver chest"
The chests with the gold lining, do not get to go into big mode. Basically they allow the client to read BIG from one itemID and not the other.
Very stupid and hopefully they fix it in the future. That being said there is nothing we can do on our end to force it. It would come on wonky and even though it would show big it would only allow you to place in the space normally allocated to that chests itemID.
UO needs to add it directly to the client, which is closed source / not something we want to modify.