Info on possibly Marshall head model 120(?)

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Comments:
: can anyone give me a better idea of what i have here and maybe how much it could be worth? : I have a really really old marshall head, i cant find any labels that say what type it is, it was made in bletchley england, and is 100 watt, it has a power switch, a standby switch and something else idk what it does,1 hi gain and 1 lo gain input, has a 1 volume nob, presence, treble, middle, low, and master. It looks like the originol "Marshall" lettering fell off and was replaced, it looks like the old Retangle Box and letters used to be there, but has now been replaced by Plastic cursive lettering, fron panel is silver looking, tubes had to be replaced a while ago. : inside it says it was assembled by Paul and tested by RV on 7/2//80 : actual amp with the input/outputs and ohm selector has a number 986 stamped in the metal housing : im not sure how much of this info is useful or not, : you can see pictures here.... : http://pic14.picturetrail.com/VOL545/2284895/4737282/61739360.jpg : http://pic14.picturetrail.com/VOL545/2284895/4737282/61739365.jpg : http://pic14.picturetrail.com/VOL545/2284895/4737282/61739358.jpg : http://pic14.picturetrail.com/VOL545/2284895/4601967/61739354.jpg