Esharp,
The differences are subtle and probably not noticeable. Both reference numbers are still "in stock" in Chopard boutiques.
The seminal model was the L.U.C 1937 Twist issued for the Chopard 150th Anniversary in 2010.
L.U.C 1937 Twist from 2010
Ref. 168527-3001 – Twist with satin-brushed silver-toned dial and red seconds hand
In 2011, two L.U.C 1937 Classic watches were launched with 42mm diameter and 11.39mm mm thickness but with the crown at the standard 3 o'clock position:
L.U.C 1937 Classic from 2011
Ref. 168544-3001 – with porcelain-type white dial
L.U.C 1937 Classic from 2011
Ref. 168544-3002 – with satin-brushed silver-toned dial and rhodiumed hands
Ref. 168558-3001 model has 42mm diameter but is thinner at 10.64 mm with silver sunburst dial marked AUTOMATIC
Regards,
MTF