Hi John This looks very much like a chassis for the 'Don Young' King
Arthur which was published in Model Engineer under the name 'ELAINE'
back in around April 1971. It is certainly similar to my 5" Arthur and
would be around the correct wheel size and spacing. The other
alternative would be LBSC S15 4-6-0 published in English Mechanics back
in 1938. I hope this is of help. Regards Robin