A few months ago I bid [in a well known on-line Auction House] what I thought was an M3 plane. Looking at the photos supplied it was obvious that the rear handle did not have a screw through the front of the toe and into the base [classic early M3 characteristics]. No dimensions were supplied ( Sounds familiar, sometimes getting important info from a seller is like getting blood from a stone!). I won the Auction, but on receiving the item, I was in for a shock. The plane was an M4 size, but on disassembly the real facts were disclosed. This plane was like no other MARPLES that I had ever seen. And, yes it was definitely a MARPLES with the Triple Shamrock cast into the base behind the Frog. The dimensions are very similar to an M4 and the main differences are in the Frog assembly and the base mating surfaces of the Frog. The whole arrangement is reminiscent of the Stanley Bedrock plane, in that the frog has a totally flat bottom, divided by a sunken area and the base has a matching configuration. The only securing feature of Frog to base is the two Frog screws, which enter the base at an angle [cf vertically in most other planes] this being due to the fact that the Frog assembly sits on the base at an angle. There is no Frog Adjusting screw assembly. The Base and Frog are both ‘painted’ Black, which is Petrol dissolvable and the ‘Y‘ Lever is Cast, with the Frog being ‘painted’ after it was totally assembled which means that the Lateral Lever rivet and ‘Y‘ lever rod ends are overpainted. On the Base both front and rear ends are clean, with no paint. The Lever Cap is stock from that era and was originally Nickel Plated, but no more. The Cap Iron has the ‘Grinding Angle’ guide configuration. The Blade is Standard at 2″ wide with an early Trefoil ‘W.Marples& Sons, Sheffield, Eng.‘ impression. The screw that holds the Cap Iron to the blade has a wide shoulder and the Lateral Level disc rotates. The Frog rivet that secures the Lateral Lever has no strengthening ring cast into the Frog on the underside. The blade holding screw and Frog screws look to be uncoated steel. The Brass Depth Adjusting wheel has 3 fine knurling lines. The mouth of the base is 1/4″ wide and the base at the front of the mouth is quite thick at 3/16″ and quite long from the cross-piece at 1/2″. The wood is BEECH, [which varies from this era, as the normal wood around this time would be Rosewood] and the rear handle retains its’ MARPLES Water Transfer on the top. So I think that this plane emanated from the R&D Dept of MARPLES around 1936 and was mostly put together from parts then available on the line, all except the handles, the Base and Frog main components.