an 'S' can sometimes look like an 8, there are times that the numbers are not completely there and there are times you have to shine a flashlight right to see the numbers. The earliest harmony made instruments I've seen were guitars made for Sears that had penciled in catalog numbers but no date codes.
I've seen this date code system back as far as 1932 personally and heard about it's use earlier. They used numbers like W34 for the Winter of 1934, S42 for the Summer of 1942, F50 for the Fall of 1950. One would be a model number, the other would be a date code. Harmony instruments generally had two stamped numbers.
