Split breech Remington with additional hole in block

[Egil]

I've found some photos of split breech.
One of them is strange.
There is a hole in block, beneath a split.



Could you explain me what the hole was made for?
Is it, maybe, kind of centerfire cartridge conversion or something else?

Thanks in advance.

[majorfs45]

The holes looks to be off center, so maybe it was for a Rimfire shell?

[Egil]

Yet, the split breech was for rimfire shell, so this hole was made for different reason.