This old gal has everything you are looking for in a Model 42 (early model, ventilated rib, skeet choke). I got this from the original owner over 15 years ago and it's been sitting in my safe ever since.
Made in 1936 with a rare ventilated rib 25" skeet barrel -- most Model 42s are plain barrel and full choke. Action is really tight with little internal wear showing. I can send more pictures via email
Could you confirm the skeet markings on the gun: on the barrel, and on the bottom of the frame? Also, please confirm the date of this gun (it would be helpful to know the first three digits of the serial number).
Serial numbers of receiver and barrel assembly match (see picture). 5 digit serial number that translates to made in 1936 on the Winchester Lookup table.
First ventilated ribs were introduced in 1954, made as two diameter round post “donut” configuration. The second configuration, a single diameter round post, occurred beginning in 1956. There was no stamping on either side of these ribs. The third variation, oval posts, had Simmons Gun Specialties stamped on the side of the rib. These began production in 1957.
The rib on this gun appears to be the last variation. Solid rib gun’s were made beginning in 1934, FWIW.