2.5mm is standard size president use for accessories like ext s meter,
in the case of the new radios I believe its 3.5mm ext speaker socket is for the new dect Liberty Speaker/Microphone,
President Liberty Wireless Mic | LIBERTY
The 2.5 mm will be for the smaller vox mic Easterbunny Online has linked too.
Again president missed the boat with the liberty mic, ideal to use the radio remotely but sadly lacking one ot two essential controls like channel change,clarifier and band change, yet again another good idea badly put into practise,
I can't see any practical use for it unless you sit on the same channel all day, channel/band/mode and clarifier control would have made it a far more useful function,The idea is good,execution of it pish poor and badly thought out unless your a one channel wonder, I'm sure podgy will be first to buy one so he can sit out the back on the 2 days of summer we get and abuse foreigners on 555. President are killing their own reputation slowly but surely.
I've been in the chippy in Saltcoates and can't say I noticed deep fired mars bars but then I wouldn't have been looking for them and I'm sure any chippy in Scotland would do them if you asked, infact I've been in all the chippys in saltcoates,stevenston and ardrossan which all lie right next to each other on the coast about 30 miles from Glasgow and can't remember seeing them advertised in any of them or in the multitude of chip shops in Glasgow, but like most Chinese or Indian takeaways here the chippies will do just about anything you ask them to do,Scots have some weird culinary tastes from munchy boxes to deep fried chocolate and the ever popular chips/cheese and curry sauce, then wonder why we have a lower life expectancy than baghdad