I'm not sure if it is proper or not... I included a folder with my cover letter, resume, reference list, official transcript, letters of recommendation, copies of my CPR/ ACLS cards, and a copy of the certificate of completion for a dysrythmia course I took. (Senior Nursing Student Applying for My First Job)
It worked. I got offered jobs at each place I applied. My cover letter listed some of the experience I had with specific diagnoses working as an extern. This sparked a conversation about the approach towards caring for this type of patient and resulted in impressed looks between interviewers after my explanation of care.