What am i??

Hi there i am new to this and was wondering if you could help me out!
we bought Diesel 6 months ago and we thought we where buying a staffie!!
The breeder said he was a pure staff but the mother was registered but the dad was not so we got no papers!!When i collected Diesel we where show his mum and she is a staff no questions asked!! But as we where promised dad was no where to be seen!!! Dont gett me wrong i would not change Diesel for the world and we all love him to bits!!! but just curouis th think what you experts think !!! He 7 months old and really big for his age... 19 inches at the sholder already and getting quite big all over but has this longer sort of ridge of hair on his back and the hair round his neck and on his tail is a little bit longer than other terriers coats i think.... i tryed to contact the deals again but they have changed there number ect..... here are some pics and let me know what you all think!!! I am 99% sure he is 100% staffie but 1 % percent is niggling away at me.... thanks for your help... cheers