Three Scottish Plaid Brooches

Good day folks

Here are three lovely plaid brooches: Royal Scots, Cameron Highlanders and Gordon Highlanders. The Cameron's is the largest with a diameter of approx 3.75 inches.

Is there a way of dating them? Or indeed any red flags as I'm making the bold assumption that they are military.

These are outside my area of collecting interest hence the stupid questions and they will be offered for sale if pukka.

Many thanks

James