The most common shielding gases used for these main arc welding processes include argon (Ar), helium (He), carbon dioxide (CO2) and oxygen (O2). While Ar, He and CO2 may be used by themselves (i.e. 100%) for certain applications, in other cases the four gases are mixed together in different combinations to form shielding gas blends.
Cluster reduction in speech is when a consonant cluster, that is two or three consonants occurring in sequence in a word (like ândâ in friend), is reduced by a child into a single consonant through omission.
FNR-Frame Noise Reduction: used to eliminate fine noises from blu-ray discs. BNR-Block Noise Reduction: used to eliminate mosiac like noises.MNR-Mosquito Noise Reduction: no idea as the abbreviation is itself so confusing. gold ring will have the gold content inscribed inside. It may  also have the manufacturer's mark inside. 5C would be the  manufacturer's mark.