set equality is not as expected

gistfile1.rkt

[email protected]> (let* ((a-box (box #f))
                               (b-box (box #f))
                               (a (set 1 a-box))
                               (b (set 1 b-box)))
                          (set-box! a-box a)
                          (set-box! b-box b)
                          (displayln a)
                          (displayln b)
                          (equal? a b))
#0=#<set: 1 #&#0#>
#0=#<set: 1 #&#0#>
#f
[email protected]> (let* ((a-box (box #f))
                               (b-box (box #f))
                               (a (list 1 a-box))
                               (b (list 1 b-box)))
                          (set-box! a-box a)
                          (set-box! b-box b)
                          (displayln a)
                          (displayln b)
                          (equal? a b))
#0=(1 #&#0#)
#0=(1 #&#0#)
#t