I have received a set of new brake shoes for my Mini. Now, I know that brake shoes have a leading and trailing edge and need to be mounted correctly. However, the shoes I have received appear to be symmetrical: I don't see a clear leading and/or trailing edge. I have attached a photo showing this. The only, minor, difference I see is how slanted the edge of the friction material is. The edge at the bottom of the photo has a slanted edge, whereas at the top it is almost square.
Is there a recommendation, or mounting instructions, on these brake shoes?