So therefore. I have the same question as you, but I would like to know exactly which IOS version the iPhone has, e.g. 9.3.4. I asked this question here but got such a useless answer. In which, yes, always download the latest version and you won't have a problem.

But your question got me thinking again, the date of manufacture ;-)
And lo and behold I have it.

As follows: Your iPhone SE, 32GB, Space Gray has IOS 10 (can also be seen in the specifications). The release date, which I assume is the same as the manufacturing date, is 24.03.2017.
The release dates of the IOS versions are now visible at https://ipsw.me. Accordingly, yours should have 10.2.1.

If you buy it, let me know if I was right:-)