Here I have taken the measured drawings, and transfered them to some 18 gauge steel. Gauge sizes are based on the number of plates which when stacked up make an inch. So 20 gauge is quite light, and 14 gauge is very heavy. Most armour is 16 to 18 gauge.
Judging solely on the size and robust nature of the hammer marks on the inside, I would expect the same on the outside, and since there are NO hammer marks on the outside, it must have been sanded away with a sanding brick. The renaissance artist who made "Laking 84" had started with something quite heavy, maybe even heavier than 16 gauge. Though it is hard to tell...the metal used in the rolling of the edge (the "roping) was clearly only about 18 gauge...perhaps it was thinned with the hammer before rolling? Or perhaps their planishing methods were so good very little sanding is needed. As an armour maker, I lean towards the sanding brick theory. Super fine planishing can only be done on a highly polished very hard anvil, and requires many thousands of overlapping light blows. The hammer marks on the Laking 84 armour were NOT made by a light hammer. The heavy hammer blows would damage the anvil pretty quickly, and not give the results required. And yet, there seemed to be no evidence that anybody had made the metal thin about half an inch from the edge to enable them to roll the edges. Because of so much hammering, the thickness of the metal changes dramatically throughout, so the question of what size the armour used to start with is pretty much moot. I do know that I can make an armour of much the same thickness and weight by using 18 gauge. As to materials...I used mild steel. The original is iron. I don't know how much carbon is in it, but it doesnt crack...it bends.
The curator who first catalogued this armour was Mr. Laking, and this was clearly the 84th item in his catalogue. Mr. Laking had made an name for himself in the London Museum, before it was amalgamated, his name keeps coming up in museums all over Europe! I believe he was heavily involved in the excavation of the Temple of Mithras in London. Regardless, his catalogue is still the catalogue used document all these look-alike armours.
The first step of course is to roll the edges to make the neck safe. I don't have to roll the arm pits...there will be special pieces fitted in there for that purpose! Those will get rolled.
The second step is to bash the steel into a hollow in the wooden block. This is actually quite satisfying. All done by hand with a big hammer...takes about 10 minutes.