When you state miniature piano do you mean a small upright with a short keyboard of maybe 3.5 octaves or 5.3 octaves? Or do you mean a small upright piano? Sometimes people use the terms in different ways.
Examples of what I consider to be small uprights are the Baldwin 6000, Heintzman 140CK, Kawai K-8, Steingraeber 138, Steinway K-52, Yamaha YUS5. For me an upright of more reasonable size would be more like 145-152cm (57-60"). (I miss the low bass on my old 57" upright. It blew away every single new piano
I have ever
played, thanks to its new bass strings, even though the hammers were worn to the core. The two 1950s Hamiltons I now have, while they sound better once you get above about an octave below middle C, just don't have the deep richness in the bass that the big upright had.
Oh... and small grands are ones smaller than the Rubenstein R-371.