Secure Mail Box or Money Deposit Safe Box SDB-200
[DHO-SDB-200]

This box does a good job. I'm using it as a rent drop for my tenants. Initially I did not know how to mount it to the concrete block so I contacted the manufacturer and all they said was "hire a general contractor". Really unhelpful. So, you can figure it out if I did, just YouTube concrete anchors. These are a little different than the standard ones, but same idea.