Here is a 48 car case. It's made of vinyl and cardboard and has 4 plastic trays to hold the cars. This was issued in 1966 and the cover depicts the #41 Ford GT.
This case was issued in 1967. It is vinyl with cardboard trays that hold 18 vehicles. The cover has the #8 Mustang.
From 1966, here is a 40 car case. This one has two trays that hold 20 cars each. Again, made from vinyl and cardboard, one side features the #6 Quarry Truck and the other side has the #53 Mercedes.
As the years went by, Matchbox got a little more creative with their cases.
Here is a 36 car case that resembles a truck from 1976. This was a gift from my wife.
Finally, I think this one is from the late 1970's or early 1980's. It holds 48 cars in 4 plastic trays. It is shaped like a race car. These come in various colors. My wife spotted this one a t a local antique store.