Hi
All fascinating stuff.
I've memorial cards from well back into the 19th century mostly but not all from Lancashire Catholic family of Irish descent. Many of them were not well off enough to afford a grave stone, but managed this type of memorial.
Many cards give genealogical information, often including the,burial place, which is often not easy to find. Many also include a prayer for the person, or a biblical quote and religious picture.
Best wishes
Emms