Interesting reg......(F)~ SN used to be for vehicles regsistered in Dunbartonshire Scotland,in the days gone by.
All started with ASN 1, BSN 1 to 999 then through the series,reversals of number and letters etc......I used to own OSN 26 ! Years ago cops could spot an odd (not of this area) reg. no,an "out of COUNTY" vehicle. Where I lived. Nearly all vehicles had the same series all ending in SN...I had a van HSN 111L, BEFORE THAT YSN 844K......now it is all changed. Glasgow reg. vehicles were mostly GB,GD,GG etc.
If a cop spotted a car driving around Glasgow, with a reg. ending in NL.....like my Morris Marina 1.8TC coupe, DNL 970K.....he would know before stopping me that the car came from Newcastle !
Just a long long time since I have seen the reg. FSN !
Just an observation........1st thing I thought was a Scottish reg. car!......not so nowadays