Block casting date.
This block/engine came out of a 68 satellite.

since I can barely make out what it says,

Is there a date here when it was machined?
There is not a stamp pad on the oil pan rail for a vin number like all 68 and earlier blocks, but also the sequence number is not stamped into the bell housing rail.
All other internals would match a 68 engine though, forged crankshaft rod journals not cross drilled and the lighter 273 rods.