This combination headbolt/spark plug wrench, embossed with N-17016 and 126809, has what appears to be a Snail Brand boss on it.  Assuming that's what it is, what did this wrench go with, an English Fordson tractor, or maybe an English Ford?

Probably Fordson- Found this on a Fordson Site-

QuoteExport Tool Kit.
N1725 Adaptor Water Ballast Valve
O1A17015  7/16x1/2 Open Ender
O1A17016  9/16x5/8 Open Ender
N17016 7/16x5/8 Wrench (Capscrew)
B17020  Screwdriver
N17021A or E1ADKN 17021   Adjustable Wrench
B17025 Pliers
N17029  Open Ender 2 3/16 Hex
E27N 17034  Handle Wheel Spanner
51 17035  Wheel Spanner
E27N 17080A  Jack Assy
E1ADDN17098 Injector Lifting Bar
E1ADDN 17017  Open Ender  3/4
E1ADKN 17018  Key 1/2" L
N 17125 or E1ADKN 17125  Grease Gun

For Petrol or Kero Tractors add-
EOA 17017 Tube Socket - Spark Plug
E27N 17022 Screwdriver/Point Gauge(Magneto)
19E 17049 Tommy Bar
N 17079  Carby Jet Key
E1ADKN 17052  Pump (Spark Plug Air)

If I remember correctly, the 'snail' was used on Fordson tractor wrenches.  I've had some Fordson stuff without the Snail so don't know the time period or the significance.

Mike

Papaw is correct.  Some time in the 30's (I believe 1937) Fordson part numbers were given the N prefix.