please help .. must the letter or support be stadmped?

I'm thinking of doing an online diploma from MIT in order to enrich my application while I'm applying to a master's program in another school.

my problem is that after completing that diploma I would get only a letter of support form MIT signed and on a letterheaded paper but would NOT be stamped - I don't know why - this letter of support would be instead of the certificate of completion.

I asked the school and unfortunately, the one who's responsible for replying the inquiries is not able to give a decisive answer.

do you think this diploma would be worth-doing without a stamped letter of support? do I exaggerate and the problem is tiny or even there is no problem it's not a must to be stamped?
any thoughts would be appreciated since I'm confused and can't take a decision and I'm running against the clock!

Ask the school where you are wanting to do the masters what they need. An official certificate should be enough.

I already messaged them and unfortunately couldn't get a decisive answer, and there is no certificate just a letter of support

Sorry I missed that bit. That's a bit odd. Do you actually need this diploma for the masters program?

yeah, it's vital for my application since it's from a reputable institution like MIT but my only fear is after spending a lot of money and effort on it they don't consider it on the other side because it's not stamped!