Laminated wood veneer was patented in 1797 although laminating hide, wood, and cloth for strength was used to make stronger shields and bows for millennia. The process became commercially available about 1865 and common by 1930 probably due to transportation infrastructure. The significance is that plywood allows for more advanced aircraft and boat designs in keeping with SteamPunk.
This is an excellent albeit DP example of why plywood is important: Mosquito Construction
Plywood is a Victorian technology that has somehow managed to stay right on the cutting edge throughout its history.
Its the whole reason for the rotary lathe, which was invented by Alfred Nobel's father. This gave france a technological edge in 1860.
In 1865, Plywood came to the united states.
The Schutte-Lanz airships were made out of it, since it was stronger than steel and lighter than aluminum, allowed for flexibility, and wasn't so dependent on regular inspection and maintenance for maximum reliability. The single biggest failure of the plywood airship was that glue technology was significantly subpar and was prone to dissolving in water (which is a bad thing for something that is supposed to operate in the rain. early fixed wing aircraft had similar issues)
Combine this with advanced engineering concepts like geodetic construction, (a concept which first made its appearance in the 1790s or so as a form of reinforcement in US sailing Frigates like the USS Constitution and was finally realized in 1911, again, with the Schutte-Lanz airships.)
It wasn't until 1934 that waterproof wood glue was developed, and the development of said glue rocked the world. The only problem at that point was a lack of industry standards for product grading and quality control. It wasn't until 1938 that the plywood industry standardized into what we know it as today.
WW2 wound up being the absolute and true baptism of fire for the wonder wood. It was plywood that filled the gap in many industries to save other materials for priority projects.