need help identifying a mark

bought an old house near the sea, found 2 metal doors with a mark on them, ill be glad for some help on identifying this.

 

I would guess that would be initials of an owners name. But just a guess. Looks like HNH and maybe another letter like k over the top?

 

Never take pictures into a bright light.

 

It looks like initials to me too but I also see a K. HNK NKH KNH etc

 

Thanks, SIS!

I've always liked the look of these monograms, but now that we're looking a one, can anyone tell me how to read them? is the largest the last? the N and K are both in front of and behind the H.

 

I see INRI

 

Thanks for the comments, but i cant find the connection of these initials.
The previous owner didnt had any of these letters in his name and none of his relatives too, any other idea what it could mean?