You can log into the Tolsma Digital Logbook here:

Each individual Tolsma Tank is registered before delivery. From that moment on, it can be recognised and monitored anywhere, anytime. Right from the start, the history of the tank is recorded in its own logbook, which remains inextricably linked to the tank throughout its entire lifetime.
The logbook contains details on maintenance, inspections and any repairs and/or modifications, so that all this information remains available even years later. Nowadays, the paper log has been replaced by a digital version. The major benefit of this is that the logbook can no longer be lost.

Paper certificates could/can easily be lost. Fortunately, it is possible to request a copy of the lost certificate.
Request copy of a certificate.