I want to purchase a "budget" (read Chinese) anvil. Contacting the manufacturer I was told I could get an alloy steel or a high carbon steel. Both have the surface hardened to 55 HRC. Which steel would be best and what percentage would be considered HIGH carbon content?

Thanks, 

Dark Horse 

Frankly, any anvil hardened to 55 RC should work fine.

"Alloy steel" is too vague to make a useful comparison. If they're charging extra for it and they won't tell you what the alloy is, it's probably just an expensive upsell.

Technically, "alloy steel" is redundant, since all steel is an alloy of carbon and iron. However, it's also used to differentiate simple carbon steel from steels with other alloying elements such as chromium, nickel, molybdenum, etc. These additional elements can add hardenability, shock resistance, abrasion resistance, toughness, etc, but there's no one "alloy steel" that does everything.

Many common alloy steels would improve hardenabiliy, permitting the face to be hardened to a greater depth.  But that would depend on the specific alloy and heat treatment technique, and might well not make a practical difference in any event. 
 

That's an excellent point, Mike. So many of these abstract questions can be answered with "It might theoretically make a difference, but the practical difference isn't worth the trouble."