Help identifying this frame's true maker

[Duae rotae]

I suspect this frame is not a Mercier. What is certain is that it began its life blue coloured and has been resprayed at some point to this colour. The bike's most discerning feature is the embossed M on the seat tube (which appears on both sides) and its decorative lug work. There is a serial on the bottom bracket which reads T 070617. There are no stud marks for any front emblem.
Any hints as to what it actually might be? I am not sure the 531 front fork would have been original to this frame. (Although maybe I've started doubting everything).

 

[non-fixie]

That looks like a Minerva frame. A Belgian manufacturer. I have seen them wearing other brand names before (although Mercier is a first).

I happen to have one, a Tuyttens (which is/was a bike shop in Mouscron, Belgium. Mine is made with Minerva "Tubi Speciali in Accaio".

 

[Duae rotae]

Wow! Many thanks @non-fixie! I would have never known. I am glad it is correctly attributed now.