I've seen more then a few of their NAV-AIDs and other products during
closet clean-outs and in "Seasoned" member's basements.
https://www.madeinchicagomuseum.com/single-post/g-felsenthal/
(https://www.madeinchicagomuseum.com/wp-content/uploads/2019/02/848e7d_7c0b91127ea94d639c9edbe24bbead51mv2_d_1778_1442_s_2-768x623.png)