Markings will be the default answer, though some models have unique features which make visual identification possible, e.g., the Yugoslav M59/66 has the gas cutoff and is set up with a grenade launcher sight and rifle grenade launcher, Chinese rifles usually have a spike bayonet for the basic Type 56 carbine, Albanian rifles have a very distinct look. If you send me an email with a photo and detailed description of the markings (my email address is posted in my profile), I'd be more than glad to identify it for you.
Take it to a gunsmith and ask for help
Between $250 and $350 for a decent one.
What you have described doesn't exist, so, it can't have a value.
To determine the year model of your SKS rifle, check the serial number located on the receiver or the barrel. This number is often accompanied by a factory code that can help identify the manufacturer and production year. You can also refer to specific SKS reference guides or online databases that correlate serial numbers with production dates. Additionally, examining any markings or features on the rifle can provide clues to its model and year.
In the context of Norinco SKS rifles, the "M" at the end of a serial number typically indicates that the firearm is a variant known as the SKS-M. This model features specific modifications, such as the ability to accept detachable magazines, distinguishing it from the standard SKS models. The "M" designation helps collectors and enthusiasts identify the specific configuration and features of the rifle.
Condition?
Value of ANY gun is based on exact make, model, and condition. A well worn Yugo SKS may be $150, while a pristine Russian SKS is $500. An average Chinese SKS is around $250-$275.
SKS made by Norinco (chinese)
Could be a Type 38
Right now, NORINCO (Peoples Republic of China) is the only current manufacturer of the SKS rifle. In the past, they've been manufactured in the former Soviet Union (Ivhesk and Tula arsenals), former Yugoslavia (Zastava), Romania, East Germany, Albania, North Korea, and North Vietnam.
Check the receiver.
Not without a detailed description of all markings and features.