We present a spectroscopic investigation on Er/Ag co-doped platelets of silicate and phosphate glasses with the aim of assessing the effect of silver as a sensitizer for erbium. The silver was added by immersing the samples, at 663 K for 67 h, in a molten salt bath of molar concentration 0.5% AgNO3 and 99.5% NaNO3. Additive heat treatments in air at different temperatures, ranging from 673 K to 773 K for 30 min and cooling in air after each anneal, were performed on both the silver-exchanged and the silver-free plates. The optical and spectroscopic features of the samples were investigated by photoluminescence measurements in the region of the 4I13/2 - 4I15/2 transition of the Er3+ ion, excitation spectra in the range from 360 to 750 nm, and absorption measurements. Increases of the Er3+ luminescence at 1.5 microns are demonstrated when the excitation is in an absorption band, located at 420 nm, possibly originating from the surface plasmon resonance of silver particles.