<VV> Carb top coating

[Sethracer at aol.com]

I think it was called an Alodine treatment. We used in on several  other 
parts on the M113 Personnel Carriers that we built. - Seth Emerson
 
Here is a link:  
http://www.aircraftspruce.com/catalog/cspages/alodine1201.php
 
 
In a message dated 7/14/2013 1:18:08 P.M. Pacific Daylight Time,  
harryyarnell at verizon.net writes:

The  factory coating was an anodizing that was more light bronze in  color.