<< this bike has a different seatlug when compared to the headlugs?>>
Ouch! That looks like a Schwinn late in the day Friday afternoon bow wow. That bottom bracket shell is not at the top of the food chain either...
This just proves (again) that the bike buoilders did not set a certain lug or frame component detail for a set time (" Phartmueller bikes used Prugnat Type S lugs in 1967 & 68") The reality is that there were likely big metal or wooden bins in which all the lugs were dumped and the worker-bee folks reached in and grabbed the first thing that thei fingers touched. Sometimes they would pull a lug out and say "Opps,. that doesn't match the others " and go back again. In this case the builder was in a lazy mood and just used what he/she had in hand...
Dale Brown
Greensboro, NC USA