The lens a small mark on the front element. It won't affect the photos in any way.
The Minolta X-300 is a 35mm manual focus SLR based on the MD mount, and which was produced between 1984 and 1990. The X-300 was also marketed as the X-370 in the U.S. and Canada.
A year after Minolta released the X-500, they introduced the X-300 to the photographic market. It was a less-expensive alternative to the X-500 thanks to fewer features. The body of the X-300 is nearly identical to that of the X-500. The only change, other than the nameplate, is that the shutter speed dial is now covered, only showing one speed at a time. In addition, the camera features are minimized. Perhaps the biggest feature change from the X-500 is that the X-300 lacks the OTF (off-the-film) flash mode -- which many find very useful. In addition, the X-300 lacks the DOF preview button, the PC connection, and the interchangeable screens of the X-500. Together, these changes reduced the price tag of the X-300 significantly.
The camera has an electronically-controlled cloth-curtain focal plane shutter. The shutter can be manually controlled stepwise from 1 second to 1/1000 via the covered dial on the top of the camera, but in aperture-priority mode, the shutter is capable of stepless speeds and can open for up to four seconds in low light.
The meter is mounted in the pentaprism, and gives a center-weighted average light value. Unlike many more expensive aperture-priority cameras, the camera does not continue metering while the shutter is open (as the mirror is up and so light is blocked from falling on the meter.) Thus, if there is a light change during or immediately before the exposure, while the mirror is up, the camera will not compensate.
Like all MD-mount cameras, the lens mount has an internal armature to stop down the diaphragm when taking a picture, as well as an external rotating ring that is moved by a stud on the lens to communicate the aperture setting. (To be precise, it indicates to the camera the difference between the lens's current setting and its maximum aperture. With TTL metering, it is not necessary for the camera to know the actual f/stop numbers, only the brightness metered at the maximum aperture and the number of stops below maximum that the lens is currently set to.)
When the shutter dial is set to "Auto," the camera is in aperture-priority mode, and will choose a shutter speed based on the light value and the aperture setting of the lens. The shutter speed is displayed in the viewfinder: when the photographer touches the contacts on the shutter-release button, a light will appear next to the shutter speed marking at the edge of the frame. An "A" for "Auto" also appears when in aperture-priority mode.
When the shutter dial is set to any other setting, an "M" appears instead of the "A" and the camera is in metered-manual mode. The camera displays a flashing light for the currently selected shutter speed and a steady light for the recommended speed (determined by the aperture). Turning the aperture or the shutter-speed dial so that the lights coincide gives proper exposure. This mode replicates the functionality of older Minolta match-needle cameras such as the SRT-101, replacing the two needles with lights. It also allows a decent analogue to shutter-speed priority operation, as the photographer is free to choose a shutter speed and then quickly match the lights just prior to taking the picture.
The camera also features an AE lock: pressing this button down locks the exposure setting for as long as it is held down. This allows the photographer to meter specific areas of the scene that would otherwise be under- or over-exposed. Pressing the AE lock button also causes the meter display to light up. The meter remains lit for 15 seconds after the photographer releases either the shutter release or the AE lock button.