Oh, you must be referring to those Gun Parts Corp (formerly Numrich Arms, NY) M98 receivers. some are described as engraved but not heat-treated. If I recall, those are actions made by Santa Barbara in Spain.
Please be advised that (and there are certainly exceptions), Spanish gun steel is generally considered to be too soft for gun receivers. For many years, they had a bad reputation for lacking durability.
I've owned several surplus Astras, Star, and Llama pistols and M93, M95, M98 Spanish Mausers, plus examined probably hundreds of others. As a rule, they are "soft", and as a rule, they required more gunsmithing attention than most other guns I've worked on. Firing pins, extractors, slides, and frames are subject to peening, burrs, and breakages, more so than most all other makes and brands.
Please don't take this as a criticism of Spanish guns in general, but merely observations made over the last 30 years of working and using firearms of every description.