Originally Posted by CWEX:
Yes the 7091 joiners are for the 2 rail Atlas track...code .148.
The 6091 is for 3 rail track....glad to be of help.
here is the link to Atlas' web page..with a picture of the 7091's
https://secure.atlasrr.com/ato1/itemdesc.asp?ic=7091&eq=&Tp=
Mystery solved for me. Thanks CWEX.