That’s a lovely MF in great condition for its age. Not that you asked but I found this incredibly comprehensive guide to Asian bike serial numbers when I was trying to date my two early S&G / Muddy Fox bikes. The earlier of the two I have is also an S&G Cycles MB~MF 26B but in silver with black decals.
Classic & Vintage - Asian Serial Number Guide - Many of you will be aware of my penchant for collecting and analyzing serial numbers. This guide compiles the results of a decade of data collection of pre-1990 Asian serial numbers. The guide is not necessarily comprehensive, as it only represents...
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It would seem to suggest you have a frame from June 1984? Although I had always assumed pre-Muddy Fox S&G brand bikes were from 1983 too. I also have a Muddy Fox Seeker from the year after our S&G models which I had assumed was a 1984 bike but the serial number suggestions it’s a 1985 bike.
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S&G has serial number stamped on the seat tube, the Muddy Fox serial number is stamped on BB shell.