It certainly appears that the gun was fitted with the earlier style Miller single selective trigger. The safety slide is now the selector. The Miller Brothers were not very neat with their whanging their R S L on some nicely engraved top tangs.

I recall reading that Parker Bros. engraved the rib legend on vent ribs for a period of time, as they had trouble with the rib standing up to the roll-stamping.

The Miller trigger is not original to the gun. Was sent to Miller for modification. R= right barrel L= left barrel & S= safe. This type of safety was not very good & were a little sloppy on holding their position. They has another selectable safety with a little rocker on the front of the trigger that was better. Besides the cracked stock, it appears the stock & barrels have been refinished.

I have a DHE 20 with the same Miller trigger and have owned the gun for close to 20 years and have never experienced any problems with the trigger. It's nice when shooting sporting clays if you want the left barrel first simply slide the safety back instead of forward.

Bruce the rib legend is correct from what I can see in the pics. Rib legends on VR guns were hand engraved as compared to roll stamping on solid rib guns. Get 2 of them side by side and you will see the difference. The receiver also appears to have a flat top further supporting the VR. The matting is without question PB to my eye. The last 3 digits of the serial # may or may not be on the underside of the rib, usually between the 2nd and 3rd post. You might need to go outside and or get a dental mirror to spot them. "FROM WHAT I CAN SEE" there is little doubt in my mind that this is a PB rib.

Additional Observations:
 

The safety was tight with no wiggle. The special order code 11 does not indicate a single trigger. Why would a selective trigger be refitted on a shotgun with identically choked tubes? Both tubes are full choke.
Of the 7 or 8 Parkers I've owned every one's inner for-end had near new remaining case color, that's not the case on this one. For that matter every other one had evidence of case color at least in the protected areas, here again this one is largely devoid of remaining case color, just subdued blotchy shadows. The butt stock finish exhibits a good amount of "crazing". The lock-up is very tight.
Given the expense to get the gun in shooting condition one has to rationalize whether it's worth it. I believe the head on the butt stock can be repaired and the rest of the gun could be left as is and it would still be a desirable gun. One could go with the "full house" restoration and end up with a very lovely shotgun. Consider that the barrels require no attention what so ever other than some oil on a rag, the expense of repairing the stock and perhaps a stock refinish would put the investment at (guessing) <$5K. In my opinion you could shop for a long long time to find another one at this price point.
One of our members has reached out and indicated that if I pass on the purchase he would like to purchase it. I have no problem with passing the details on to the Library Manager. This means there is at one person that thinks this example is worth the time and investment. As always I appreciate everyone's help here.

Why would a Miller single selective trigger be added?: Because it's what the owner wanted. The dead giveaway is the engraved "SAFE" from the factory is still there & the safe position lines up with the stamped "S". If it was special ordered with the Miller selective trigger there would be no engraved "SAFE" position. Only the R,L,S. I'd say that about 95% of the Miller triggers on Parkers were sent back to Miller by the owners. They were much simpler than the Parker single triggers & were pretty reliable. You can still have Miller trigger installed today, but they no longer do the selective trigger on the top tang. Only the little rocker selective on the front of the trigger. I've owned several of each & the selector of the front of the trigger was a more positive setup

Ithaca Gun Co. used the Miller single selective trigger on their NIDs from their introduction until the 1932-3 time frame when they went to their Harry Howland Patent knock-off of the Miller. Both using the safety slide selector. In my experience that is the only selector I could possibly make a decision with on a flush. Guess I might be able to make a decision with the safety/selector on a Remington Model 3200.

Since both barrels measure exactly the same, full & full what possible purpose would a selective trigger make? Using the left barrel for a bird flying left? It seems redundant to have a choice when both barrels are choked identically. What am I missing here?

The owner probably just preferred a single trigger gun, selective or not and probably just had that particular one installed?

Okay, makes perfect sense. I've shot double trigger shotguns for over 50 years and it's a perfectly natural instinct for me. I just hadn't thought about someone preferring a single trigger. On a side note, I recently learned I am intolerant to coffee. Going about my daily routines without coffee, I'm pretty sure it's having a negative effect on my aging brain function. :vconfused: