This image shows two signatures made by "a" man named George Cox. One signature is on an Army Attestation Form when a boy of 15 signed-up in 1900. The other comes from a 1922 Migration Application by a man of 36.
Addition: I chose not to date the signatures because I thought it might bias your view. If I was wrong, see the comment below.
I have a WWI Service Number for the 1922 Cox which led to a Medal Card but his other records have not been found. (Many WWI records were destroyed in WWII bombing.)
My interest in the 1900 Cox arises from the fact that the 1922 Cox went from being an insurance salesman on 3 August 1914 to being part of the first mobilisation on 14 August and then the front line of the Battle of Mons on 23 August with the Royal Scots Fusiliers. I infer that this was unlikely unless he was a former Regular soldier. I then began a search for pre-war service records.
The 1900 form shows an age (in years and months) but no precise date of birth. That age is close, but not an exact match for a calculation from the d.o.b given in 1922.
I need to decide if the two signatures are sufficiently similar to justify further investigation of the 1900 Cox.
(As an aside, the 1900 Cox trained as an army bandsman and the 1922 Cox had strong connections to the Salvation Army. Proves nothing, but ...?)
I have taken up the suggestion of @Rob Hoare to make a collection of signatures from the 1911 Census. Here are six of the approximately 1100 George Cox recorded in England and Wales.
The impact of rigid schooling on how people wrote their name is quite evident. Clearly matching the signature on the back of a credit card would have been much easier 100 years ago.