Presented below are some reference photos of screen-used combadges ...
A combadge from ST: The Next Generation. Note the inset velcro on the reverse establishes the piece as a later season version. The early TNG combadges did not feature recessed velcro design but simply placed velcro on a completely smooth back surface.
This Deep Space 9 Bajoran combadge is composed of metal. Both metal and resin Bajoran pieces were used on the show.
A Voyager combadge, obtained with a screen used Seven of Nine brown catsuit, that was worn by actress Jeri Ryan ...
Another combadge, originally from the collection of TNG, DS9 and Voyager Senior Illustrator/designer Rick Sternbach ...