The PM-55 is a version of standard Warsaw Pact MT-55 bridging system. The bridge is normallly carried on a T-55 tank chassis, but the PM-55 uses a variant of the Tatra 813 cross-country truck that could carry and deploy the bridge.
Wikipedia has a
short article about the MT-55. A Czech forum has an extensive
collection of photographs of the bridge-laying truck in action.
This item consists of two trucks and two deployed bridges. A separate model of the
truck in action, deploying the bridge is also available.
Other Warsaw Pact engineering equipment can be found at
Luke Ueda Sarson's shop