Help with identifying this "Cinelli" bike frame

Start by contacting Cinelli with your frame's serial number, and whatever details you've got, like country of origin.

UK: https://www.cinellibicycles.co.uk/contact/
Italy: https://cinelli.it/en/contact-us/
US: https://www.cinelli-usa.com/contact-us/

I would suspect its a `90s bike based on the fat frame tubes, back when Aluminium frames were overbuilt to account for the material properties of AL.

It may have had downtube shifters, but those bosses were also a normal fixture for integrated brifters.

---

The Maxzone headset is out of place - that brand seems to have origins in the Philippines. Decidedly a long way from Italy. I suspect this is more of a local replacement rather than an original part.

We can't see details of the outboard BB, but presume its been replaced too.

The frame clearly has a derailleur hanger, possibly non-replaceable, but can't really tell. Whereas googling "cinelli mash" returns a lot of single speed and fixed gear stuff from the 2010-2020 period. So I presume that MASH was something and has been "pivoted" to single-speeds because of trends.
Or its a sticker/decal that someone has slapped on the frame.

---

The only thing that puts me off the frame is that horrendous weld around the headstrap reinforcement. It looks like painted bubblegum, and while I have no welding skills, that looks janky.

If you give it a good inspection all over, and see no damage then its probably okay to ride. As long as the frame's a good size for you and not damaged, and seems like quality then whether its "real cinelli" or "Chinelly" doesn't matter that much.

Ultimately, you need to guess the cost of all the other parts you'll need, and the cost of the frame/fork, and see how that total compares to buying a complete bike, either new or used. And availability comes into it too, this post-C19 world has some messed up supply lines.