SL212480 might be the engine serial number for a service engine, but it is not a serial number for a 5000 engine from the 1000-series period (1965-75), which had serial numbers beginning with R or E.
There might be date codes in the other areas I marked. If it is a service engine, there might be a sticker on the valve cover.
Are you able to post some pictures, showing the engine and the tractor (if it is on a tractor)?