I could never figure out the foundry those 110-Ms came from. I tried like heck to find the RC marking on other parts and failed. Maybe someone who knows casting really well would be able to identify that. At the time I wasn't trained on the Reynolds and Reynolds/RUMBA green screens to find all the suppliers, and depended on other folks to look that info up.

In normal old world MP fashion (using basically the same logic as paint marks which usually failed to identify cams) they weren't date coded. The only indication of a rough date of manufacture was on the box, or the yellow sticker on the crate engine they came on.

I do know the 110-Ms actually had two machine shops at the end of their run, which I thought was weird.
Cummins recon did their machining in-house for crate engines, and the parts heads had somewhere else.
Say what you will about Cummins recon (And you would be right), but the seats pretty much never fell out of crate engine heads. I can't defend them as they had other issues besides that, but they did get that one detail right.
If anyone is lucky enough to have never heard of this rightfully earned folklore, you're very fortunate to have not wasted any time on it LOL.

When 110-M's were phased out I hoarded a few sets, some with more issues than others.
Some are in beautiful shape, some have issues that required welding, and I bet you can guess the rest.
I didn't use them and went with Victor Jr instead, this thread helps explain some of the reasons why LOL.
That stuff I collected will probably get sold cheap to someone local.

You know, I am going to act like an old guy and point at history for a minute.
I'm pretty sure 300cfm @ .600 was probably considered outrageous and amazing airflow....................in 1964.
From that perspective, they kinda do what they are supposed to do.
They're like a stock replacement head in aluminum, sort of.
Well, the iron heads were never that ugly but I'm talking from a functional standpoint.

From a modern perspective,110-Ms basically HAVE TO be ported and well prepped... preferably by a pro...to stand a chance at keeping up. Having Porter Racing heads go through them was definitely a good move.