Agreed with Wayne. It looks like it might be from a later 1930’s Speedster where they did not attach a serial number tag to the top panel of the tank. For instance, in this picture of a model 905 Special Speedster (1931-33) you can see that it used a tank similar to the one you have there. So, it may be an Elto tank – just not the right one. but if it works…run with it.
Hope this helps.
Best,
PM T2
He's livin' in his own private Idaho..... I hope to go out quietly in my sleep, like my grand-dad did..... and not screaming, like the passengers in his car...