Attached to this post are 3 links,
They are of current ads advertising case 155's. Depending on availability, also dictates prices. The one link, shows a restored case 155, nice looking little tractor but for me, that one would seem to be on the high side, The other 2 links, would be in the "general range" of the one you posted about. The lowest priced one, from what I can see, would require a bunch of work,,,
It's been pointed out to me that apparently around your region these are very common and lots are available for sale. Using a search engine, I couldn't seem to come up with much around Michigan at this time. Maybe others, could post some links to give you a representation of pricing,,
Are all of the pieces there, (front grill, front panels) as indicated earlier, finding parts for these, at least for me, has been a bit of a challenge. Nothing that I haven't over come, but regardless, still a bit of a chore.
FYI-- Perhaps others will chime in, but to fully restore one like this, (others as well, ie Case, Deere's, Craftsman's, ect, in other words, all brands) costs way more then you'll ever sell it for. That's to do it correctly, and just not slapping lipstick on it, and calling it restored! So, something restored, is a keeper for yourself, something you can use, without having to work on it every time you go to use it. It is something you like doing and enjoy the end result, not for resale because there is no money in that! (if you have thoughts of doing a restoration)
Lastly, to answer your question, the number on the side, would seem to be a bit oversized. Compare it to the restored one in the link and you'll see a difference. The restored one, if you look at it closely, seats appear correct, the muffler appears correct as well.
2 - 155 Case Lawn Tractors
J.I. CASE 155
1967 case 155 lawn tractor