It is a diode but no marking at all, except the cathode band. Please help.
It appears to be an 0805 case (you can confirm with a ruler). If I look at current Digikey offerings there are only Schottky 1A diodes in that package, however the package is not the same (has castellated ends).
I can, however, find offshore 1N4148 equivalent with an identical looking package so that might be a good guess.
You can desolder it and measure the Vf at some reasonable current, and thus rule out Schottky diodes. You may be able to measure the capacitance which will rule out many rectifier type diodes.
The inexpensive Chinese LCR component measuring devices show 3pF on a regular 1N4148 and Vf = 691mV. Schottky diodes will measure much less Vf and rectifiers will generally measure much more than 3pF capacitance.
Of course it could be something else like a varicap diode, if you know something about the circuit you may be able to figure it out.