Hi, guys,
First off, Franzite was a very popular brand of after-market grips in the 1940's -1960's. "Franzite" was a trademark for the material (plastic) as well as the Chicago company, which was named after the owner, whose last name was Franz. They made simulated pearl, ivory, onyx, walnut, and maybe others. The light grips (pearl and ivory) had a bad habit of turning yellow or absorbing color from adjacent objects, like a box lining.
They were pretty fair grips for a reasonable price, though obviously not original on the HP.
Be cautious of wartime HP's. The Belgians "forgot" to do the proper heat treatment when they could get away with it. I have seen several wartime HP's with barrel lugs so soft they battered and stopped the gun after less than two magazines. Some slides are also soft, as are slide stops. I would retire that HP to collection status and buy another gun for shooting.
(For some reason, some folks don't believe this, and I have been called a liar or worse for saying bad things about the glorious HP. I fail to see how sabotaged wartime production reflects on pre- or post-war guns, but some people think any criticism of their favorite gun is cause for a fight.)
Jim