Hold on (you'll get there), yer still on the wrong side I believe. He described it very well - Pass. Side. - a letter/ number /letter /letter like U have (C1XX & C9XX). U may hafta get a flash lite, bucket of solvent (gas, kero, commercial degreaser) & a brush like I did. Scrub it up then wipe it down.
"...the pump is missing..."
might mean the fuel pump
the C prob means "196X" and the 1 could mean "1961". If U get on the correct side (ie the right side sittin on the seat) there is a second number almost touching but below the CXXX number. 4 numbers a hyphen & a letter The last letter tells us if it's a 170 or what. This is my understanding anyway. Give it a try, nothing to loose...