Munster regiment - The most common copy has a really fat and broad Tiger compared to the originals. The fakes come with both sliders but also with 2 horozontial lugs. While the older Victorian ones did have lugs but these were N to S (ie up and down) in my experience where as the copies often are E-W across the width of the flames on the greande. Look for the brazing holes on the reverse for the original bi-metal ones. There are lots of fake 1916 all brass ones but again with a fat tiger and the shorter slider common to the repro.

Leister regiment - If it does not have 4 brazing holes on the back don't touch it. The slider is also longer than the copies ones which stop at the base of the badge - they are heavy solid badges but lack the brazing holes. The 1916 all brass fakes have this same slider and are in a very yellowish metal.

Royal Irish - Faked to death often with JR Gaunt.London mark. The originals tended to have voided strings on the harp (although Wilkinson's book does have a solid stringed one), long slider and a hole under the crown with a U shaped brass strengthening wire behind it. The copies sliders are shorter than most originals and stop at the bottom of the badge. Also they often have solid strings as this is easier for the faker to make.

Connaught Rangers - As above.

Inniskilling regiment - On the WW1 badges the flag afced to the left while post 1934 it flew to the right. I remain to be convinced by any RH flag in all brass is a genuine example. Look for the brazing holes on both types but later RH flag were siometimes made without them. However one of the common fakes have a falw in that the flag does not stand clear of the castle. The originals are only comnnected by the metal of the flag pole where as one of the common fakers dies has extra metal here so the flag is not cut out clearly but has a line dropping from the bottom edge of the flag. Clear to see when you are looking for it. As an aside the a/a versions with lugs are not cap badges at all but are still worn on the kilts of the RIRISH pipers and are still in production.

Tyneside Irish - Actually a shoulder title (soem collectors have a view that it was worn in the cap at some time in the war) so should not have a slider but lugs and a void under the crown. Commonly faked with a slider bearing the JRGaunt.London mark.

Royal Irish Fusiliers - The best way of spotting an original is to check for a brazing hole on the reverse of the grenade and often a strenthening strip behind the neck of the grenade. The a/a lugged versions are again a kilt badge and not a cap badge which should be slidered.

Royal Dublin Fusiliers - the most obvious give away is  with the detail of the tiger and elephant on the front as the original stend to be much more sharply definer.  There are poor copies with a separate tilte scroll where as the originals tended to have overlaid scrolls often (but not always) with brazing holes.  The brass reverse behind the scroll has been solid rather than dies struck on the examaples I have seen.

Hope this helps you spot the rogue sellers and cheats.