0x007102 = 100.000000
0x00350C = 500.000000
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0x0C3500 = 0x027100 * 5, so the byte order is reversed.

0x027100 = 160000, so maybe packed = 1600 * unpacked?

0x300515 / 1600 =? 860.99  Yes!
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Solution:

my $raw = 0x300515;
my $val = unpack('N', "\x00".pack('V', $raw))/1600
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or

my $raw  = "\x30\x05\x15";
my $val = unpack('V', "$raw\x00")/1600;
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