Pedersoli 1861 Springfield Rear Sight

I was hoping that another member may have some insight into this rear sight blade arrangement on my Pedersoli 1861 Springfield rifled musket. The 300 yard leaf is a no-brainer but the slot on the 500 yard leaf is an enigma. Notice it also has a hole which I assume is a calibrated sight/range hole for sighting. Pedersoli has not answered any of my three emails asking for clarification on this rear sight. None of their literature or web images show this particular sight leaf arrangement with a slot on the 500 yard leaf. Have any of you seen this before and used it?

Attachment 292554 Attachment 292555 Attachment 292556

Once you have a good load I'd just shoot it and see where it goes. There are so many variables in loading that the factory sights seldom are right.
Normally you would get some blank sight blades and calibrate them to your own personal load so it hits where you want it to.

I have shot musket in the N-SSA for over 40 years, only time I shoot further than 100 yards is at our annual local Turkey shoot.

I would say 400 yards zero.

I have had Springfields and Enfields in .577-.58 caliber and to get a good 100 yard zero, with standard load of 500 gr Minie ball and 60 gr of FFg, the point of aim/impact @ 50 yards was about 5-7 inches high.

4 to 5 inch groups for five shots @ 100 yards was always my benchmark. (Others can probably do better)

I've never seen an original sight of any kind with that type of slot/hole. "Maybe'', just maybe it's a 300M sight for European competition, but that's just a guess on my part.

I wonder if it could be some sort of stadia? I will have to find somebody brave enough to stand out there and let me point my rifle at them. No worries - I'm not Alec Baldwin whose gun fires with immaculate ejection.