an initial attempt
We start in classic form with
or, from the command line,
dc -e "[[dc -e ]P8795PP93P[dx]P8714P]dx"
[ ] quotes
- → the ending dx produces the classic quine pattern of code preceded by its quotation.
P prints an integer in base-256/ascii
- → quotation characters can be avoided by entering strings as base-10 numbers
For example, 6120568 == 0x5D6478 == "]dx", and so by punning between the numeric and string representations of a value, we reach...
 the final result
This quine duplicates 6581840, printing it once as the number 6581840, and once as the string "dnP".
Most invocations of P in the quotation-using quines occur immediately after their arguments. Can you spot the P that is used to print the entire outer quotation?
 historical note
These days, using a literal both for its numeric value and its executable potential is unlikely to be found, outside of a quine. (inside of a quine, it's too dark to code) But back in the days of bit-bumming, when short registers and deep latencies made programmers miserly, Mel, a Real Programmer, and his peers were fond of them:
"You never know where it's going to put things", he explained, "so you'd have to use separate constants". It was a long time before I understood that remark. Since Mel knew the numerical value of every operation code, and assigned his own drum addresses, every instruction he wrote could also be considered a numerical constant.