Clarinets commonly use two keys for their instrument - Bb and A. However, Cornets, the lead melody section in concert bands and brass bands, only seem to use a Cornet in Bb. This would be normal - after all, there is no Trumpet in A - but I have found records of Cornets in A existing.
Recently I was looking at the score for Elgar's Land of Hope and Glory. The opening clearly shows a brass section of 4 Horns in F, 2 Trumpets in F, 2 Cornets in A, 3 Trombones and a Tuba.
Secondly, the ABRSM Music Theory in Practice: Grade 5 book shows it. The transposition chapter includes transposition practice for Clarinet in A and Cornet in A.
So, are these instruments widely available? Is there any use for them over the standard Bb Cornet?