ALRO slide rule chart Cor-V-mat medical ECG-calculator 1970 Holland

One very interesting hybrid calculator for reading ECG scans and making various determinations from them. There is a whee mounted between 4 studs set through the rule, capturing the wheel between 2 transparant sheets. It is signed with Cor-V-mat name as is the plastic sleeve and the Dutch manual. Credited to a Dutch Professor D.H.G. Keulenmans (born in 1915) and made by the Dutch slide rule Company of ALRO (which stands for ALl ROund) who in the late 1960’s decided to expend into the production of slide charts and other (non round) calculation aids. Guesstimating this slide rule being from the 1970’s while the ECG scan being around from ca. 1900 (read about the history of the ECG here). The slide chart and all it’s part are in good condition with normal signs of use only. It measure ca. 25 cm or 10 inches high. Check the attached video on how to work your vintage man tool : slide rule operation instructions!