250 Chott rear sprocket measurements

[growler]

Has anybody got dimensions for Chott rear sprocket - B&C express (UK) don’t now make them and didn’t keep info
I require a 520 38 tooth but need bore and hole dimensions to get made

 

[growler]

Anybody?, help with question above.
Summers here and riding Chott most days so don’t want to strip until got replacement