It is not too small to matter it is to big to be taken seriously by anyone working in advanced science at the time. Your quoted date of 1893 is three years after Lord Rayleigh had done his experiment, which I did at school and I am sure many forum members did, dropping a droplet of camphor oil onto water covered in lycopodium powder, this typically estimates the size of a Camphor molecule as 1.7nanometers. As I remember my physics teacher telling me, the accuracy doesnt matter, at the time no one had any idea how big or small an atom or molecule was, if it is wrong by a factor of ten it was far too small for anyone to consider measuring with the methods they had in 1890. Johnson Matthey in London produced 30 bars of 90% platinum and 10% iridium and in 1889 bar number 6 was accepted as the closest to the prototype meter standard selected in 1799
The standard metre copy you describe when the USA took the metre standard was numbered copy bar no No 27, it deviated from the standard metre by 1.6 microns.
To summarise this part, while Angstrom was developing his Angstrom unit in the mid 1800s discussing measurements of 10 to the power minus 10 metres (10 to the power minus 7 mm) the world standards based on bars of metal couldn't produce reliable metal samples of a metre to better than 0.01mm, or 10 microns. In aerodynamics in the 1930s and 1940s companies like de Havilland and North American were discussing surface finish of 2 microns for polished aluminium and 5 microns for a good paint finish. Testing a paint surface for thickness and smoothness could induce irregularities or 1 to two microns. All of these measurements are below or in the ball park of the difference between the USA standard metre and the official standard held by in Paris by the
Mètre des Archives).
As an inspector of 30 years working in metrology and other things I ca see the fundamental and unavoidable mistake made by the people concerned in the period 1799 and 1893, recognised by any person with a scientific background, can you?
Your point was made with respect to de Havilland ordering or supervising production of their Mosquito design in the USA. The Mosquito can stand beside the P-51 as being at the top of aircraft design. For choice of aerofoil, cooling drag regime and surface cleanliness and overall low drag design they are on par by their own route and path, they have almost nothing in common other than with the same engine both were approx. 30 MPH faster than a Spitfire with the same engine.
As a company de Havilland could build you an engine pre and post war, build you a metal or wooden aeroplane, they designed their own suspension for the Mosquito based on compressed rubber good enough to cope with massive overload on recon versions and also carrier landings. They manufactured propellers under license from Hamilton in USA, produced their own hydraulic and electrically actuated propellers even developed phenol-formaldehyde resins which were half the weight of aluminium for propeller blades. The notion that de Havilland could not cope with any metrology issues between USA and UK is just funny, in a very funny way. I really don't know where you get your ideas from.