S31 was not a number station. It was Czech(oslovak) army testing its equipment by sending test counts. Last heard in 2000 after more than 30 years of operation.

The frequency 1122 kHz had test counts from 50 to 59 every hour from sunrise to sunset in the minutes 10 to 12, and 40 to 42. No intro was used.

The frequency 2136 kHz had test counts from 50 to 59 daily at 18:45 CEST. The transmissions started with nine tones in three sets of three.

The test counts were played from a tape.

[Based on this page, and Numbers & Oddities #19]