In an attempt to add some information on the tunnels cataloged 1938 through 1941, I examined my original catalogs.
The 1938 catalog lists tunnels
242 - 10.5 inches
247 - 11 inches
248 - 15 inches
The catalog shows an illustration of 1 tunnel and these tunnels appear to be the same tunnels from the 1935-1937 era, which would make sense as there were probably unsold items when Gilbert purchased the company in 1938.
The 1939 - 1941 catalogs lists the following tunnels:
247 - 11 inches
248 - 14 inches
The illustration shows a tunnel similar to Bob B's tunnel pictured above.
Again, this is where it gets confusing as Gilbert seems to have re-used the same numbers for different tunnels.
NWL
