Is This Great Britain Machin Definitive Photogravure Or Lithography?

Good Afternoon, I'm new to determining printing methods, needed to organise my GB Machin definitives.



The stamp here is a 2p from the Stanley Gibbons "X" series, and I believe the colour is described as "deep green" in "Collect British Stamps" (CBS). Following the guidance in CBS I'm looking for wavy edge to value. The Value below looks relatively smooth to me so I would think lithography.

My problem is that I believe this should also apply to the solid background as it runs to the white perforation margin; This is obviously composed of dots of ink.

So... I'm confused! What's going one here?

Is it SG X927 (photogravure by Harrison and Sons) or SG X1050 (lithography by Walsall), or is it something else?

Cheers, Dave

I am by no means an expert on Machins but yours looks definitely
printed offset litho.
Below are a couple of my 2p, photogravure on left and lithography
on right.

Thanks for your reply, lithograving.

I think litho is the conclusion I am leaning towards.

As I understand it, a screen is still needed for the parts of the image that has shading, as you can see over The Queen's portrait. Perhaps the printer decided to fade the edge of background as it approached the perforations, rather than having a sharp edge, requiring a screen and appearance of dots.

Dave