“Inhb” short for “Inhalt” or “Inhabe” (German) which means Contents or Contains. Can’t see it on your pic’s but I’d guess there was a pressure there somewhere.

“Prob” (date) is again German for “Probieren/Probiert” meaning testing/tested – So you have the original Test Date.

Looks like you have a fully dual-language Gas Bottle marked in English and German. It looks like the original marks were the English as they seem to be in the “right” place

…could’ve been used for anything.