The original back sight would have been a fixed standard (150 metres?) and a folding leaf for 300 meters or thereabouts.
The standard would have obscured much of your field of view with the Lyman, which is no doubt why it was removed.
When I fitted (thanks to Roger Hale!) a Parker-Hale cocking piece peep sight to my 9.5 x 57 I drifted out the original sight which now lives in a pot in the case.
I was fortunate to find a spare sight, and dressed down the standard to a flat bar level with the top of the folded 300 meter leaf. It does not obstruct the aim, and the folding leaf provides a useful reference to check the windage adjustment on the peep sight.