The caption says that it was extracted from his grave in Offenbach when the old cemetery was razed in 1866, and is owned by Emil Pirazzi. The image is from Alexander Kraushar's book, Frank i frankiści polscy, 1726-1816 Vol. 2 , as is the one below, which is different from the usual depiction of Frank:
Here's a creepy crown ornament of some kind taken from his coffin (he died in 1791). Looks like filigree, maybe.
There's also an image of his daughter and successor Eva:
And a document from 1793 with her signature: