helmet dist extension button

[blackchevy3de]

I have a 39 ford 59ab flat head when replacing the dist I found that it had a extension between the dist and cam , is this stock , or what dose is meen

 

[smallfoot]

Some info on this site mentions a couple of distributor changes. Maybe some answers can be found on yours here:

http://www.vanpeltsales.com/FH_web/flathead_specs-85to100mid.htm