galaxies observed with HST in the cluster of galaxies ${\rm CL}\,0024+016$, at $z = 0.4$. Such a similarity is a clue that G may be an elliptical galaxy at $z\sim 0.4$.

Gravitational lens models
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As an application of the astrometry and photometry of §3, we attempted to estimate parameters of lens models that accounted for the following observed properties of : (1) the relative coordinates $x_i$ and $y_i$ of the images of the core and of the center of brightness of G ($i =$ A1, A2, B, C and G); (2) the ratios of core image fluxes $F_i/F_j$, with $i,j =$ A1, A2, B and C for $i< j$; and (3) the shape and location of the arc.

It is likely that stars in G do not affect the radio flux ratios by microlensing (Witt, Mao & Schechter 1995, hereafter WMS95). As in other lensed systems (e.g., 2237+0305, see Falco et al. 1996, and references therein), the optical flux ratios are probably affected by microlensing. Indeed, the optical and radio flux ratios are quite different (e.g., KH93): for example, the ratio A1/A2 is $\sim 2.0$ in $I$ (see Table 3), and $\sim 1.1$ at 8 GHz. We attempted to 