ZentRa is a West German watch containing the Porta PUW 2501. The case, with is all stainless steel, has unusual styling!
The Porta PUW 2501 has a Transistorized Controlled, Moving Coil movement. PUW 2500 was without date or day; PUW 2501 is with date and PUW 2502 with day and date. All three were only produced for a short period.