1949 mod 18 rigid rear mudguard brackets

[Invicta]

Please can anyone assist with how the rear mudguard brackets are fixed to the plain rear mudguard on a 1949 model 18. Are they riveted, bolted or welded ? I have looked at photographs on the net and can not see any rivets or bolt heads. On my 1950 with ribbed guards they are welded or brazed. I am fitting an Indian made rear guard and have had to remove the brackets, which were riveted, to put them in the correct places and now I need to secure them where they should be and would like to do it the way that AJS did it originally . Thanks.