The square Euros came stock on higher end models such as the 280/E/CE/TE, even on the W123's early years. The round Euros came stock on lower end models. Which ones were considered high end and which ones were low end (how high, or how low?), is still unclear.

Some models had vacuum leveling adjustment, others had a mechanical style adjustment, to compensate for vehicle load. These are supplementary to the beam pattern adjustment one performs to adjust the lights correctly.

There are also those with amber fog lamp reflectors, which are typically called "French" spec lights (forum slang). This is because they were popular in France when amber fogs were mandated, IIRC. The "French" spec Euros came in both low-spec and high spec variants.

I believe all Euro lights had city light function, but the headlamp wiring depended upon country of registration.