Wall shucks, after all them yars some young whippersnapper of a girl, no less, has ruined the song for me:

"It doesn't have to be the thing you're buried in; in the song, it's apparently a keepsake or jewelry box and not, actually, the coffin."

Thank you Scoville kid!!

Muttterin' to hisself: and I thot she was awaitin' for her sister to put her in the casket (coffin) sittin' on a marble stand when she kicked the bucket..

I like my varsion better so a coffin hit will be and the letters can juss be from a durn letter box or snuff can.