1880 With No Grade Stamp on Water Table?

[Juliet Thomas]

New Parker owner here,

I just came into possession of an 1880 under lifter (serial no. 194XX) and spent a good deal of time attempting to identify it. Though I was stumped when I couldn't find a grade mark on the water table. Although I have identified the serial number and found a Letter "C" marked on the face of the barrel lug. I've found one other example on the web of a 1878 with very similar markings but no definitive answer of what specific grade the gun is.

I've attached some pictures that can help identify it. Thanks all in advance for your wisdom.