A nice used example of an U.S. M1 fixed bale helmet. The helmet has been applied with yellow line and red triangle 'TTU'. 'TTU' standing for Tank Training Unit. The unit provided specialized training for soldiers and non-commisioned offers. The helmet is fitted with original M1 liner. The liner has been applied with the same unit marking. The liner is makers marked 'International Molded Plastics'. An interesting U.S. M1 Fixed Bale Helmet not often encountered.