1978 450SEL 6.9 Battery Draining

[Hexaflouride]

After driving 1400 miles round trip out to South Dakota I have my first gasser! I've been working though the neglect and doing all the basic maintenance stuff. One issue I'm stuck on is the battery drains when the car is off. Yesterday I put a multi meter between the battery negative and the negative cable and found that 0.37 Amps is constantly being drawn when the car is off. I pulled all the fuses and it was still drawing 0.37 Amps! I don't really know where to look next. Are there any fuse boxes other than the one in the engine bay? Are there any circuits on the W116 chassis that are prone to draining the battery?