Some of this will state the obvious to many here, But, Just to get all the terms straight. On the pad there is a Engine ID code and sometimes a VIN code. In this case the engine has a sort of "VIN code" or CE code. Sources on the web say CE was "Chevrolet Engine" and they quote a GM bulletin dated 14 April, 1969, but don't show a copy of the bulletin. Supposedly partial VIN codes on engines were Federally mandated Jan1, 1968 and were stamped in various places.
The other number is the Engine ID code. An engine ID code has a Alpha Suffix Code on the end (of course) which gives the applications for that engine. In the case of the posters stamping, it seems the suffix was bastardized due to unknown future usage. There is no XTD or TD code (maybe XTB= To be Determined)
Next, the ports are holes on the side of the head. (intake and exhaust). Ports are sometimes called peanut, oval and square. These are not to be confused with valve size (Values given as diameter of the valve opening IE: 1.94 or 2.02, etc).
