A 1920s Peterborough tram ticket.
“WKM” was ‘Workman’s Return’, which was a type of fare for early morning workers. It was cheaper than an ‘Ordinary Return’ (which is the “ORD”) in that you could travel further for your money.
The cheaper ‘Workman’s Return’ seemed to be a tram or trolleybus in most towns and cities and was done away with when diesel buses took over.
The “W” on the sides is just a place for the conductor to clip a hole for a Workmans fare, and “R” for an ordinary Return.
In the case of this ticket, it is a 6d single ‘In’ being an inward journey towards town.
A return ticket would be punched on each side, once on each leg of the round trip.