difference between Winchester model 90 and model 6

Grandma’s .22 has fallen into my hands. It would be a great collectible if Dad hadn’t had the barrel replaced and the stocks refinished sometime in the last 50 years. I first thought it was a model 90 because the (newer) barrel clearly says ‘Model 90’ and .22 long.

I took it to a gunsmith today who suggested it was perhaps a model 6 with a model 90 replacement barrel.

Is there any decent way to tell the difference between the two models so I have a better idea of what I have? Other then the round barrel stating its a model 90, I have no other reason to think one or the other.

It does seem to cycle and shoot .22 long rifle so, I think, that could mean its a model 6. Also the forestock appears to be fit for a round barrel, not an octagonal one original to a 90.

The serial number is 608643 which would put it built in 1918 if its a model 90 or 1923 if its a model 6…both are very plausible for the family history for this particular rifle.

Any experts want to help me determine if its one model or the other?