B6 Side Belt/Zip

[blueleader]

My RMNZ B6 with side belt arrived last month and it's prompted me to think why some had the side belts and others the zipper.

Does anyone know the reason for the two different styles?
Was it a earlier vs latter design?

Cheers,
Richard

 

[Roughwear]

The side zippers are on the earlier Aero contracts. Side belts were used by Aero on later 1942 contracts and Poughkeepsie used them on their 1943 contract. My guess is it was more cost effective and quicker to fit the belts than the zip, but others here may know more.