Penny Reds Advise Needed

Hi have begun to go through my mum's stamps that were last looked at over 40 years ago.
l have found 4 penny reds, after lot of searches I have learnt a tiny bit, I can't see a plate number on them, seems some didn't have them?
I am trying to get to grips with the numbers in the corners, research seems to suggest that if there is BA AB on a single stamp it is of interest also if there are 4 B's on a stamp,
Does anyone know more about these stamps please that may help me?

There is no good reason for that. It could be that a certain plate may have a variety in that position. As a general rule, there is nothing of (extra) interest for any letter combination.

If there are letters in all four corners, there must be a plate number on each side. The two lower letters indicate the sheet position. The letters at the top are in reversed order. If there are 'stars' in the upper corners and not letters, there will not be a visible plate number.

Corner letters are
Row 1: AA, AB, ..., AL
Row 2: BA, BB, ..., BL
...
Row 20: TA, TB, ..., TL,

giving 20 x 12 = 240 penny stamps in a sheet. Each row has 12, with a total face value of a shilling. 20 rows adding to 240 pence = 20 shillings = £ 1.

Best, you post a scan of each of your Penny Reds. If you do not have a scanner, please, no hand-held pictures. Use a raised surface to support your phone over the stamp. Enlarge and focus the camera before taking a picture.

Thanks, I will attempt to put pics up as would love to see if anyone can find plate numbers

This shows plate nr. 206 in the white boxes.

Here are my stamps.

The first thing to note is that you have two different types of stamps. Note that the first and last do not have letters in all four corners. The other two have plate numbers where NSK has shown you to look. What do you see there?

Hint: I think I see 143 on one of them.

What do you mean about plate numbers I can't see any in the edges?
I know I have 2 different types,

NSK has given you a perfect example. These numbers are very small and your stamps are a dirty mess. Magnification may be needed to tell what the numbers are but I can see that they are there.

And the bottom stamp is a different issue.

Is there a way to clean sta ps as just used a macro lense & still can't see them but I do have eye disease hence why I'm asking for the forums help

Soak them in clean water. If your ultimate question is of financial value, these are likely to be worth pennies.

The 1st & last stamp are different issues to the middle 2, l am just trying g to learn about what I have, the research so far has given me the basis but I can't see the nu bers on the edges so I'm a bit stuck as to how to move forward with research, if any of that makes sense?
I do appreciate the help offered, thankyou

No it's not about money, this collection has a personal meaning, just want to learn about them & understand it

Some collectors try to find examples with their own initials, but overall this slight extra demand is random.

Partime which one is 143 please?