Интересно, что в нём перевозили?

These trams were there to grind the rails.
On the front of the tram you can read "railslijpwagen".
Inside you can expect to find all the equipment to do this (liquids / machines).

Thank you for your answer, focus1965!

По превью был похож на 80-й выльник.

These cars could work separate or coupled together