The bed frame was originally a bunk bed probably bought from Boing surplus, we're guessing, by my father in law back in the 60's. I made it into a trundle last year and it was used maybe 3 times, the mattresses are like new. We just don't need it anymore.
It works well. The lower bed slides out on wheels and raises up to make a king bed. I thought the mattresses were 3" but it measures 5" and they go with the bed.