Doesn't have the normal CE stamp but I am not sure any of the aluminum blocks did.
I would say that's probably because most of the blocks we see were over the counter service items with no info stamped on them. But I'd have to bow to what William and/or Kurt have to say about CE ZL1 blocks.
Ed
Fact is there probably weren't many warranty claims on them. Over half were raced, voiding the warranty. About 10 lost the original engine fairly soon through a swap or theft.
I know of two warranty failures on street-driven ZL1s: #55 and #69. #55 has a known history and scuffed a piston. I believe it got a warranty short-block; the original was not scrapped and is back with the car. Back in the '80s when I was chasing them I spoke to the new car manager at Huebner Chev, who ordered #69. Said it sat around for months, they put stripes & mags on it and it finally sold. Towed in a day or so later with a fragged engine. He distinctly remembered receiving an entire ZL1 engine in a crate to repair it. It's possible it was serviced with another ML engine. A few years ago an ML ZL1 engine was discovered w/o VIN. There were 54 ML engines built; 47 were used in production.
The warranty period began when the car was sold; some ZL1 Camaros weren't sold until 1970. Chevy had to service those cars until the mid-'70s. They produced far more ZL1 engines than needed for production so it is possible a few were retained for warranty obligations.