Need info on 2-ton

I have a 2-ton and need to know an approxamite year. The serial number tag has been removed. Is it stamped anywhere else? One distinquishing trait of my machine is that the air cleaner bolts to the right side of the hood. In my early Caterpillar/Holt /Best ads around 1922-23 the pictures of the T-35 show the air cleaner bolted to the side. Is this true? and if so what are some more distiquishing factures that I can use to age this machine?
It is currently in the shop awaiting restoration. Of course so isn't my 30 with winter package!