EICO portable vacuum tube tester

This is my (newer) old vacuum tube/electron tube tester, model #625 manufactured by EICO (Electronic Instrument COmpany) of New York. As a 'portable' device, this tester could have been found either on the workbench at a TV and radio repair shop, or carried in a repairman's service truck for house calls. To operate it, one would find the correct "tube number" of the suspect tube listed on the rolling scroll at the lower front (it moves up and down with the brownish knob to its RH side) which then gives the proper settings for the rest of the various knobs and switches. Then the tube would be plugged into its matching socket and the tester turned on, after a short time for the tube to warm up, the large silver button at lower RH corner would be used to perform 2 different types of 'test' on the tube, displaying the results with the large meter and indicator lights.

I don't know for certain, but am guessing this tester dates from the 1950's to early 1960's. As far as I know it is still operational, but I haven't tried to use it for at least 25yrs. No doubt it might need some recalibration by now, if nothing else...?? :-)