A known plunger for use in manufacturing glass containers comprises a first portion to contact with a gob of molten glass, and a second portion, whereby at least the first portion is coated with a metal coating of a self-fluxing alloy. Starting therefrom, to provide an improved,easy and cost-effective producible coated plunger for use in manufacturing glass containers with an improved wear, corrosion and thermal fatigue resistance and an increased lifetime, it is suggested according to the invention that the self-fluxing alloy is a Fe-based alloy containing at least 15wt. % Co, and whereby the micro hardness of the metal coating is in the range between 300 HV0.3 and 900 HV0.3, whereby the Fe-based alloy is an Iron Cobalt Chromium alloy comprising (in wt. %, balance = Fe) formula (I) whereby the Fe-based alloy may be further alloyed with additional metals selected from the group consisting of Al, Mn, Nb, S, Ti, V, Zn and Zr, whereby the individual amount of each of the additional metals ranges from 0.01 wt. % to about 2 wt. % and whereby the overall content of the additional metals is less than 10 wt. %.