What is this? Obviously old, religious - shadowbox? Icon? Age?

I found this at a thrift store today. I can tell it has age (along with gorgeous wood!), but that's it.
Is it a Icon?
A shadow box?
Is it from a church? - what was the purpose for the little cupboard/storage space at the bottom?
How old is it?
It measures 13.5"W x 23.5"H x 4"D
Thanks all - I'd be in trouble without this place & you'all with my taste in old & unusual!!

 

https://www.worthpoint.com/worthopedia/religious-antique-blessed-thy-holy-1816615675

 

This person is referring to it as a "Last Rites" circa 1909:

https://tinyurl.com/6hurddhh

 

The candle holders that flank left and right went AWOL on yours.

 

Thank you!
I've had several crosses that slid open and inside were candles, holy water/oil & linen - I was told they used to be in motel & hotel rooms back in the day so in case a person had a heart attack, etc.. someone could perform the last rites with them & save their soul!

 

it's an interesting item

 

https://www.worthpoint.com/worthopedia/excl-1913-antique-viaticum-catholic-1823711380