From the Historic knitting list on Yahoo groups - it would have been quite authentic to have either a strand of white, which might pick up some blue dye from washing/felting processess, or have old, faded yarn compined with new, so as to make a two tone tweedy effect.

However - it would not have been authentic to have anything obviously crochet - it is quite a recent inovation.

I have used crochet and then felted it so that the stitches were no longer visible, but the yarn was thinner and it was all double crochet in English, single crochet in US terms.

It is, though a rather nice item, and I'd say just wear it an your blue days - I have a whole range of berets black, green, purplish, etc and must do one for the blue/black camoflage material I just bought on eBay.