Rossi's 23 could be plucked out of the air, or it could be a sum of all the plumbers, electricians, etc Rossi has been using over the last 12 months. And remember also all those naive PhDs like Gullstrom. Charisma and tall stories will get you a long way!
To get closer to the 23 count I'd add his condo pool boy and gardener, plus the postman and the pizza delivery guys.
Also locating the lab where the test should have be performed are sometime kinda fuzzy in his head.
I well remember one of his patents addendum inviting 'patent observers in a lab made available by Physic's University department of Bologna but at the end turned out to be his usual industrial shed nearby.
(Too lazy to find this funny piece of Rossi's history - I'm kindly asking Ahlfors to get it handy)