Agreed, the flip large is zeroed for 300yds with Mk VII 174Gr ball. If you're using anything else its a bit of a crap shoot, you'll have to work out your own drop tables though.

Personally I don't hunt, but I've found out that a 180 Gr SP is close enough for government work at any sane hunting range (under 300 yds).

The small is 600 yds so you'd have to aim off way low.

If it were me I'd get a Stamped Mk4 The one with the lever curving INWARDS. There's another version curving outwards but it was well known for snagging on things & changing the range unbeknownst to the shooter, & its accompanying spacer. (There's also one with a stamped elevator, but a cast base, you won't need the spacer for that if you can find one).

The peep is about the same as the "L" & it lets you quickly dial in for longer ranges with the slider whilst giving you a better 200yd zero!.

IMO its the best balance between the very basic simple "L" & the Singer micrometer with its bunches of clicks. You just squeeze, slide & release in 100 yd increments!

The sights in the above photo are the factory issued sights.

The sight you are referring to with the windage adjustment is an aftermarket setup...

There are basically 2 windage adjustable rear sights if you ignore all the "target model" aftermarkets like the Parker-Hale & BSA ones.

One bolts to the elevator of the Mark 1 micrometer, giving you windage, but effectively removing the inscribed range scales.

The other is basically a modified Mk1 but it requires permanent & non-reversable modifications to the receiver to fit or work.

For zeroing some form of windage adjustment is a good thing. Please not I said "zeroing" not "sighting in", which is a slightly different thing.

But IMO its a "set it & forget it" kind of thing.

Now, if you're shooting paper for tiny groups centered on the X-Ring at a known distance then yes its handy.

This allows me to fold the peep sight down and out of the way when the scope is in use. The large ghost ring helps to maintaining target acquisition while the intended target is in motion in my honest opinion...

P-H4 post war production and was only made for about two or three years before Parker Hale drew inspiration from the AJ Parker 4/47 and made the P-H5c. 

Sadly they come with a collectors price tag these days and regularly fetch £300 ($335) in good condition. 

Pictures nicked from Ebay! 

Strangely Brown, Thanks for your tip-off! Didn't realize that these had any value. Now removed from my junk box!

Glad to be of service Terry! 

P-H4's are getting to be a scarce sight these days; I don't think I have ever seen one on a rifle at Bisley as the majority of SR"b" shooters I've known prefer the later, (and arguably better) AJP 4/47's and 

P-H5c's. 

Awesome!