Some suggestions from what comes to mind at this late hour. I'll no doubt think of others as soon as I log off, but it's way past my bed time as I write this!
anyway here goes...
Germany
All DB Class 218 B-B diesels: Whilst the 218s were built in the 1970s the concept of the V160 family is from the late 1950s.
France
Most of the oldest stuff on SNCF has been sidelined in the last 5 years although the surviving Paris area BB17000 electrics are a 1960s design.
However there is lots of interest to be found in France’s narrow gauge and mountain railways. Starting with the youngest (1950s!):
There is a fascinating pocket of surviving 1950s trains in the Alps. The Chamonix – Montenvers (Mer de Glace) and Tramway du Mont Blanc mountain lines are geographically close to each other and both still 100% operated by trains built in 1954 (CM ) and 1956 (TMB)
Amazingly, two lines in the Pyrenees knock the 1950s stuff into a cocked hat – with stock over 100 years old in regular use.
The La Rhune rack railway uses 3-phase Rowan type locos built in 1912, and the Ligne de Cerdagne, aka Petit train Jaune uses stock dating from 1909 (albeit partly rebodied) .
Switzerland
A lot of modernisation here as with everywhere else, but with a few older designs still in use but on their last legs (eg RBe540 power cars (1950s design).
Likewise the iconic Re4/4II electric locos – a 1960s design - are beginning to decline – albeit versions of the same thing are in daily use deep into Germany and some are being rebuilt for extended further use in the Zürich area
A lot of modernisation in recent years on the extensive Swiss private and narrow gauge network has sidelined loads of older stuff, but there are pockets of ancientness to be found.
The Pilatus Bahn mountain railway (the steepest rack railway in the world) uses single cars dating from 1937.
Tucked away in the Jura mountains are the unusual for Switzerland Italian built railcars on Le Locle – Les Brenets . They were built in 1950.
Basel tramways still uses a few 1960s Swiss standard motor trams (and a good number of trailers of the same deign) (the last Swiss city to do so.