Please Help- UK,1924-6, 1/2 D. , Large Letters.

I need some help on this SG 105, U.K.,1924-6, 1/2 d. green stamp.
The size of the inscription HALF PENNY , the two numbers at top are larger . The letters of the text above the portait of KGV are thinner and the space between outern frame and the image in center is wider.
The green line of the outern frame looks thinner. Lines in the portait are more les visible . Stanley Gibbons catalog tells tath there are two different types at some of the stamps from previous issues . The catalog attributes such difference for the 2d value, from the same issue but it doesn't mention nothing about a similar variety for the 1/2 d. green stamp.

Have you checked the watermarks?
If so, what are they?
Always try to offer best information (perf guaging and watermarks)
for accurate ID

I'm sorry I didn't mentioned this information in my first post.
I checked them as you've suggested . It seems tath both have a regular watermarks. The perforation measures 15 x 14. The color of the first one is little suspicious,it's more light than usual.Could it be a forgerie ?

Supply a scan with both stamps side by side.

There are numerous shades, and two different watermarks, for this issue.

Under-inking?

Of cours there are many small color variations of the 1924, 1/2 d ,but the difference in the size of the letters and the numbers is the tink which bothers me at this stamp. I'm posting a image of the back of the stamps side by side as rod222 suggested.

Not ideal for me.
The reason I asked for the two stamps front on, side by side is simple.
The easiest way to identify a variety, is to crop two identical stamps
scanned at the same dpi, crop to their frame then "Toggle" the images.

Any minute differences can be identified
Two stamps scanned at different dpi, or differing machines,
can make them appear irregular.

You appear to have differing Watermarks, I think one was used for coils.

Danko ,it's difficult for me to say is this some type of variety or the unusual aperence of the stamp has been caused by under-inking.

Rod the information you're posting about the watermark is interesting,but I can't still explain why is there so large difference between the two stamps on the face side . I tink I saw a stamp very similar to the first one with the large letters some time ago on the internet. I will have to search it again .

That's what it looks like to me.

post pe

If you look at the stamp, you can see that it has consistently more white and less green throughout the stamp. This is why your white letters are bigger and green letters are smaller. This is caused by less ink being absorbed into or transferred to the paper. There are two simple cases for that - under inking or less pressure applied. There is also a possibility of poorly finished paper to cause this, whether just a patch on the roll/sheet or the entire roll. The answer usually is the simplest one, so my guess is under inking.

I see three major components: plate, ink, and paper. Each with variables.
Why not consider the plate? As an engraved plate wears, the grooves become shallower and narrower. A stamp from a fresh plate would naturally show wider lines than a stamp from a plate ready for retirement. This was a workhorse stamp for many years. I would challenge anyone to make hundreds of millions of copies over the span of use which all looked identical.

They, both are Block Cypher. The stamp on the right seen from the back looks to have a different watermark but is the upright block cypher. It appears there is something at the centre that makes it look different. However, you can see the letters are not in any way like a script. Consequently, it must be block cypher. There is only one type of this stamp with this watermark. Both appear sheet stamps.

There is nothing strange about any of the letters in the design.

The stamp is extremely pale. Either it has been bleached or, as people suggested, it is under-inked.