Both badges are, IMO, from the same period of mid-late war and both appear to be made of steel. The time difference, if any, is quite small I would guess.
The first one you show has a flatwire catch and a regular sized no.'4'. The second one has the roundwire '?' shaped catch and you will note that the no.'4' is thinner in definition and size. This is known in collecting circles as the "small 4" type. Both the regular and small '4' badges can be found with either type of catch, and this is what makes me think they were probably produced side by side or at least in a very close timeline where production may have overlapped.
It's a fair guess that at the stage of the war that these badges were produced, the manufacturer would use whatever hardware materials they could get their hands on.
'I do not think we can hope for any better thing now.
We shall stick it out to the end, but we are getting weaker of course, and the end cannot be far.
It seems a pity, but I do not think I can write more. R. SCOTT.
Last Entry - For God's sake look after our people.'
In memory of Capt. Robert Falcon Scott, Edward Wilson, Henry Bowers, Lawrence Oates and Edgar Evans. South Pole Expedition, 30th March 1912.
Do not see any problem with them.
Very nice ones.