C:perl -MYAPE::Regex::Explain -e " print YAPE::Regex::Explain->new(qr/(^.* #[A-Z]*\d+.*$)/)->explain();"
The regular expression:

(?-imsx:(^.* #[A-Z]*\d+.*$))

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  (                        group and capture to \1:   
   # NB: I did NOT need the parens as there's no use of the capture
   # My bad, but harmless except for shoving bits &amp bytes around
   # when they didn't need to be disturbed.
----------------------------------------------------------------------
    ^                        the beginning of the string
----------------------------------------------------------------------
    .*                       any character except \n (0 or more times
                             (matching the most amount possible))
----------------------------------------------------------------------
     #                       ' #'
----------------------------------------------------------------------
    [A-Z]*                   any character of: 'A' to 'Z' (0 or more
                             times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \d+                      digits (0-9) (1 or more times (matching
                             the most amount possible))
----------------------------------------------------------------------
    .*                       any character except \n (0 or more times
                             (matching the most amount possible))
----------------------------------------------------------------------
    $                        before an optional \n, and the end of
                             the string
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

<p>And the output is thus:</p>

<c>C:1149716.pl

$data matches regex

TRAY HINGED PLSTC 20 CAV #F32473


         The data, BOX HSC,35-3/4X17-1/4 X 50-1/2  SIMULATOR TALL BOX, does NOT MATCH


$data matches regex

PAD, FOAM, 24 X 24 X 1/4 #16193 112 SHEETS PER ROLL, ORDER IN FULL ROLLS


$data matches regex

PKG LIST,ASST ARM,RAD,300 #F37784


$data matches regex

PAD, TOP CAP RE17-30048 #F30121 CORRUGATED ASSEMBLY, 22-7/8 X 21-1/8 X 4-3/4


$data matches regex

foo bar #379460 best F11


         The data, F1234 SIMULATION, does NOT MATCH