What I have seen in the panels over the years:
Mud dabber nest, dead bugs, bottle caps, rusted parts, extra breakers, screwdrivers, flash light, tapes, transformers, misc. parts, Mr. Lincoln hiding behind fuses, an iPhone, splices done with electrical tape, staples, ink pens, pencils, keys, zip ties and extra wire nuts.
One breaker panel had five different manufactures breakers in it, they I checked out and were compatible.
I prefer that the electrician open the panel, don't want to be responsible for any of his stuff!