Questions About Inps Stamp

I have this stamp in my collection for the INPS, with is Italy's social security agency. I have seen this a bit online but the catalogs I have seen don't have a lot of info on these. Curious as to what these are used for and when it was issued. I'm also curious as to the significance of the letter and Roman numeral as well and the text DATA. Others I have seen have a different letter, numeral, and text so it seems like they have different uses? Any info would be greatly appreciated.

"Data" : italian for "date"

(not mine)