While I was reluctant to opine, something about the fabric seems to me to pre-WW2, so WW1 might be right. Though you might have seen similar cloth used state side early in WW2. If 4 sources were paralleling regiments that would mean pre-WW2 when the USA went from a square division of 2 Brigades of 2 Regiments to triangular with 3 regiments.
I know that colour reproduction can be haphazard even with the best cameras and photographers, but the shade is not one usually I associate with WW2. The speckled colouring and coarse weave suggests wool with older, less fast or fade resistant dyes. Again suggesting pre-WW2, might well be WW1.
Take all that with a large quantity of salt, those are just vague impressions and niggles of mine.
I know that colour reproduction can be haphazard even with the best cameras and photographers, but the shade is not one usually I associate with WW2. The speckled colouring and coarse weave suggests wool with older, less fast or fade resistant dyes. Again suggesting pre-WW2, might well be WW1.
Take all that with a large quantity of salt, those are just vague impressions and niggles of mine.