Not Marin. Looks to be a fairly low end frame judging by the rack mounts, kick stand mount and dynamo bracket. Not worth a lot, would build into a heavy but solid bike
A quick weight will also reveal if it's worth saving. My guess is that's over 3.5kg...and therefore gas pipe. Such bikes can ride nicely though and make excellent transport.
A basic frame works ok - but if you festoon it with matching cheap components, it will break - so the value of a build kit worth using way exceeds the cost of a nice old frame
I agree about the headset cups, which is funny because they have capped the brake bosses and derailleur mounting prior to painting which shows some attention to detail - then they left the headset cups pressed all the way in and painted it with more runs than Viv Richards.
Not sure on the brand or model - the welds look like the TIG robot was in training. Decent forged dropouts though - not stamped.
@6puket - is it for 26" wheels? It does look like a bit like a hybrid/commuter with the rack mount, fender mounts and kickstand.