Joined: Jan 2010
Posts: 9,813
Likes: 1,790
From: Northern California
Bikes: Cheltenham-Pedersen racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
Looks like the equivalent of a UO8 so likely seamed tubing and with thick enough walls to still be pretty strong for road riding.
Examples from France and Austria have been favorites of mine, this one has a great look to it.
Lower-tier Shimano derailers from the mid-'70's make good replacements for fragile Simplex gear imo.
I cleaned up a Titlist rear derailer recently and found it to shift really well over a 13-28t freewheel, looked good to even on my Bianchi Nuovo Racing beater.