It is referred to as an 'alignment mark', the print on it being in reverse because the instruments used to check said alignment might have an odd number of mirr

It is referred to as an 'alignment mark', the print on it being in reverse because the instruments used to check said alignment might have an odd number of mirrors which would cause the image to be non-reversed. I'd say the purpose of the strip to be to align the stage either in relation to the other stages or to the launching platform.