Aging, without labels, is always difficult - if not impossible.
Certain things, like iridescent surface decorated pieces, do have known dating and can be dated without a label (very early). Muted colours are often associated with post war pieces, but that is by no means full proof.
Therefore, unless Gary, or someone else, has recorded the colourway and it has a known period you have a problem. My hunch
it has the quality of pre-war, but lets see who else pops by.........