FYI:
(Lot 11 Vintage Mechanical Pencils 1930s–60s Wearever Eberhard Faber Keystone USA | eBay)
History:
(J.S. Staedtler twist lock drafting leadholders | Leadholder - The Drafting Pencil Museum)
(Leadholder Catalogs: Charles Bruning Co., 1936, page 216 | Leadholder - The Drafting Pencil Museum)
Coming to a mailbox near me…
I saw the listing last night and offerd him some $ for just the 1018…he bit…one of my fave models
I didn’t know that website, it’s very good, I think I’ll have hours of fun.
Best thing ever for leadholders…too bad Dennis “vanished” and ceased updating it…such a great resource…
If not @lsd300 would have the four leadholders in the ad, then who would? 
He passes away long ago…
Was afraid of that…had a few nice contacts with him …always very helpful aside from the data on the site
