Hello, Corrado 
 
The "faithful" was a method used by the Spanish to fix cylindrical pieces, instead of proceeding to thread them, particularly with the frizen screw, so that it would not move, turn or come out. LAVIN mentions them in his work 
 
Thanks for the photo and for replying. 
 
Affectionately
		 
		
		
		
		
		
		
		
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