Including "Thanks Card" in my graduate application
Honestly - unless this card is speaking to something very particular and relevant to your statement of purpose I would not include it. Think about this from the perspective of someone reviewing your application. In most US grad school applications, you need to have people provide letters of reference. What would this thank you note contribute in addition to those letters?
You don't say whether you have a letter of reference from this internship, but it would be odd either way.
If you don't have a reference letter from the internship, someone looking at your application might be confused by it, and not know how to judge it. It might raise questions such as &quot;why is this person including this letter from their co-workers when they don't have a letter of reference from it?&quot;
I will also say - generally the more specific a recommendation letter can be, the better it is. Maybe it depends on thank you letter, but in my experience, those tend to be &quot;thanks for a great summer, great to get to know you&quot; which is probably of less interest to an application reader than &quot;During the 3 months Danny worked here, he worked on projects X, Y, and Z, and made contributions U, V, and W&quot;
Anonymous Physicist is right. Show the letter to the person writing your recommendation letter, don't include it in your application.