My First Post Including 2 Revenue Stamps

Hello. This is my first post. I think these stamps are pre-1940. The two Half Crowns have different shades though, so am not sure.

Welcome Muks

All four are postage stamps from Great Britain. Three from King George 5th and the other of King George 6th coronation in 1937.

The half-crown stamps are commonly referred to as seahorse stamps and are considered one of the most attractive stamps ever issued by many collectors.

The top stamp at right, has a PARCEL cancellation.
Possibly rubber or felt hammer, (Geoff? Nigel?)
W.D.O. = London Western District Office (I think)

The Blue stamp is King George V 1912
It came about (I think) due to the public disapproval of the KGV "Downey Head" design, of the previous year 1911.

Did the colours on the right stamp fade with age?

For the 2s6d, there are different shades of brown...sepia, pale, olive, chocolate and reddish browns. They are definitely not Waterlow printing which has the crossed lines behind the king's head, so they are either De La Rue or Bradbury & Wilkinson. If the height of these two stamps do not measure 22.5mm to 23mm, they are printed by de la rue. The one on the right looks like a reddish brown to me so it is printed by Bradbury, carrying a catalogue value of just £40 in fine used condition. Since the condition is poor with a heavy cancellation, it is probably worth under £5.

Thank you for the patience and explanation.