This si the handy swing out polarising filter & lens hood combo for the E43 size 50mm f1.4 version 1 & 2 summilux M lens from 1950s to 1970s.  The hood is very similar in style to the expensive XOOIM hood and can be used as a regular lens hood simply by removing the filter glass.

Leica 13351 swing out Pola filter & hoodforE43 50/1.4 M lens