Hi,
Yes, I agree it is probably made up from an old hat, as a costume, with trims added. The jewel looks 1950s as Jonathan pointed out. Also, the ribbons and jewel just don't look "right" from a millinery standpoint, the jewel button just sort of sits there....and mixing low quality marabou and faux fur is an odd combination. Plus the interior sewing is pretty shabby, not done by a professional hat maker.
The hat started out as a simple velveteen (?) 1950-1960s hat. Look at the interior...the material used for the base was not seen in hats made prior to 1948...it is a fabric/material (patterned satin bonded to buckram) used commonly in 1950s hats up through the 1960's.
B