Hi,

Yes, it sure looks like a Robbe Mäxi (Maexi).
It was a rather popular model in the first half of 1970th. Was avaliable as an all balsa kit, glass fuselage+built up wing+stab and glass fuselage+foam wing+stab. Is available as ARF today (glow or electric). I like Robbe Mäxi outline and it flies rather good as far as I know.
Images below from Robbe catalog (in German but pictures will show orginal model rather fine I think).
I have been looking rather long time for an unbuilt Robbe Mäxi with glass fuselage+foam wing+stab and actually had one in reach on ebay once but the seller withdraw the kit for some reason from the auction (I did bid on it). They are rather rare but can be built from plans of course (I have Robbe Mäxi all wood balsa kit plans so it would be possible to build one that way). Nice plane You have by the way. It seems You have the Mäxi FH version (glass fuselage with conventional built up wing+stab). Mäxi has a wingspan of 57.5 inch (1460 millimeter). Images below is from Robbe catalog 1970 (the first image to the left) and 1977 (rest, except Mäxi ARFpictures and kit box pictures).

/Bo