American Flyer either started using a new supplier in 1925, or their supplier changed its manufacturing style. The 1925 and 1926 catalogs list the same tunnels, in 2 separate columns.
The first column is the newer style tunnels and describes the tunnels as "Hand Moulded Plaster Cement"
4255 - an 18 inch long tunnel for standard gauge
4256 - a 22 inch long tunnel for standard gauge
251 - an 8.5 inch tunnel for O gauge
252 - a 10 inch long tunnel for O gauge
253 - a 14.5 inch long tunnel for O gauge
254 - a 17 inch long tunnel for O gauge
The second column appears to be the older style tunnels, as described in my previous posts. I base this on the tunnel numbers, but they tunnels are described as "Moulded Papier Mache" and are listed as
81 - 9 inches
82 - 10 inches
83 - 14.75 inches
84 - 18 inches
86 - 16.5 inches
The 1925-1926 Dealer's price lists further notes the older tunnels to be "Type A" and the newer tunnels to be "Type K"
So here are some pictures of the 4255 Tunnel. I will say that I cannot date these tunnels to a specific year, but I suspect that the second version (with the vegetation) would be the earliest version and the one below (with the box) is a later version.
Below is another 4255 variation, this one with vegetation (applied sponges)
I have not observed a 4256 tunnel, but suspect it looks similar, but longer.
