||This slide rule looks very normal,
but has special names for the scales (e.g. OF/OZ instead of A/B). Otto
van Poelje guessed that OF and OZ meant "Oben-Fest" and "Oben-Ziehen".
Also the help text for the decimal point is
different in this slide rula. On the goniometric scales there is some
help text for placing the decimal point.