Adjustable drop-outs '30ies.
ER probably referring to Etablissements Ravat. A racebike from the stable Ravat/Wonder.
Also Automoto seems to have experimented with adjustable drop-outs in that period.
In the '80ies Gios had its own version.
And also nowadays there are many forms of adjustable drop-outs in various 
disciplines of cycling.
 

Saver from Chalon-sur-Saône.
Many features of Wonder Cycles in St.-Etienne.
Presumably Saver gave his own touch to the Wonder Cycles,
a common practice of all times ... 
Project: lining, other rims and tires, adjusting the gear mechanisme

Vintage Versol Record 1950's derailleur.
A 'copy' of the first edition of the Campagnolo Cambio Corsa.

Balilla Corsa 61 Brakes Set
Related to Giovanni Galli Company from Torino.
 

PEK Belgian race bike from Couillet (Charleroi)
presumably mid/late '40ies 

SR (Sakae/Ringyo) Road Champion Handlebar

SR Sakae/Ringyo seatpost Royal-P1 

(Custom Melt Forging)

SR (Sakae/Ringyo) seatpost black RY P1-SL

Vintage Kessels Main D'or from the 70's
High-end bike, Dura-Ace group

 Vintage Merckx De Rosa Fiat Tour de France 1977.
The current owner, who bought the bike directly from Eddy Merckx in the late '70ies, recieved confirmation from Mr Eddy Merckx about the 
authenticity of the frame. Contact with Mr De Rosa learned that this bike
can be dated in 1977. All sizes and dimensions were measured by Mr. Ludwig Wynants who certified another Merckx bike in de Koers! museum.They proved to match perfectly with the certified bicycles of Eddy Merckx.