  We present UrQMD predictions for the comparison of the recently measured
Ag+Ag and Au+Au runs at a beam energy of $E_\mathrm{lab}$ = 1.23~$A$GeV
explored by the HADES experiment. To this aim, different centrality definitions
are investigated: We suggest that in the case of particle production, both
systems should be compared at the same number of participating nucleons, while
for a comparison of the (elliptic) flow, a selection on the initial state
eccentricity - as in high energy reaction - is better suited. Generally, we
find good agreement between both system, if these centrality criteria are used.
Specifically, the deuteron yields per participant and the pion to proton ratios
are shown to scale with $A_\mathrm{part}$ except for very central Ag+Ag
reactions due to stronger stopping in such reactions. The elliptic flow in both
systems follows inital state eccentricity scaling, albeit with the opposite
sign as compared to high energies, suggesting a strong relation between final
flows and the initial state also at the low energies explored here. The
observation of this scaling might then allow to obtain further information on
the expansion properties (and the EoS) of matter at high baryon densities.
