Out on the web someplace (sorry I don't have a link anymore) there is a copy of the 1966 Herters catalog. They cover their different scales pretty well (from a description and marketing standpoint). If yours is one of the M5 model with 4 leveling screws it sounds like a top of the line with accuracy to 1/20th grain. Their other models are described as having at least two leveling screws and need to be level in both directions, hence the cross bubble level. They stress the importance of having good knife edges on the pivot so check them for evenness and no pits etc. One paragraph mentions a drop of oil in the knife pivot to help keep wear down.
They had both magnetic and oil dampened models but don't mention what grade oil to use- I would guess a lightweight sewing machine or 3-in-One grade oil, as back in the 60's all the different specialty oils weren't generally available.
Herters was the Sears of reloading gear and although inexpensive, made some good stuff so that scale should be a good find for the price.
They also mention there were rubber feet and the leveling screws had rubber tips to help dampen vibrations. There might be a 'flag' looking thing sticking up on the left behind the pointer, that is their patented quick stabilizer - they mention a quick touch with your finger gets the beam to settle down quickly.
The one thing I don't see is how you zero-calibrate the pan to the scale. With RCBS the pan has a removable bottom to add lead shot when calibrating zero.
