[Milsurplus] BC-611 case screw and MWO questions

[Mike Morrow]

I've looked at several BC-611 units over the past few years and seen a different type of screw holding the top plate down on each.  My only such unit has a natural-metal-finish binder head screw with external tooth lock washer, but I've seen:

(1) Flat head screw (?!?)
(2) Round head screw
(3) Binder head screw with head diameter well less than the diameter of the countersunk hole in the top plate
(4) Binder head screw in OD green finish
(5) Screws with and/or without lock washer.

Has anyone seen enough of these sets to describe the "official, as-manufactured" top plate screw?  I assume that none of these top plate screws had a capture device to prevent separation and loss of the screw from the top plate.

My BC-611-F shows a red painted date of APR 56 on it.  That seems awful late for such a set to still be in service.

My BC-611-F has markings indicating that MWO SIG 11-235-7 was performed on it.  My 1945 dated TM 11-235 only describes MWOs up to "-5."  I'd be interested in knowing what MWOs later than "-5" did.

Thanks.

Mike / KK5F