A narrow rubber strip is given a defined pre-slit, creating two "legs".
Chemists use tear strength data to adjust rubber compounds. If a material fails the DIN 53507 test, it might indicate poor dispersion of fillers (like carbon black or silica) or a curing process that left the material brittle. Without standardized testing, formulators are flying blind. din 53507 pdf
If you search for on most free document sharing sites, you will likely find a scanned copy from the 1980s or 1990s. Do not use it for formal compliance. A narrow rubber strip is given a defined