|Serial number||NMI-7"NMI" can not be assigned to a declared number type with value -7.|
- 7 & #8. NMI. Two units of similar construction but different size. Both units have numbers stamped on brass plug entry: #7 has 3540 on top and #8 has 2530 on bottom. Bottom plates are attached with rivets. Removal of brass plug exposes soldered connections.