I couldn't say, but I think that you will have better results tailoring the size of your side plate to your lock rather than just copying an original. Also, even if the pictures are intended as full-sized, it is always possible that the photography and printing process has produced some small discrepancies - Track of the Wolf's catalog with the "exact size" pictures is not 100% accurate either.
I'd also imagine that there was some variance in the originals as well.