Is the Electron Orbital g-Factor Equal to 1 Exactly?

An important question addressed by Kusch et al in their pioneering experiments may be put as follows: If the electron g-factors are assumed corrected such that $g_L =1+\delta _L $ and$g_S =2+\delta _S $, what are the measurable magnitudes of $\delta _L $and $\delta _S $? To answer this question, Kusch et al used the resonance Zeeman technique with which they measured the quantity$\delta _S -2\delta _L =a_{SL}$. At that time, no independent value of $\delta _S \,\,\mbox{or}\,\,\delta _L $was available, hence it was not possible to separately determine the two unknowns ($\delta _L ,\,\delta _S )$. It was a practical necessity therefore to assume a value for one in order to determine the other, hence it was assumed that $\delta _L =0$. However, six decades have passed since Kusch et al skillfully measured the quantity $a_{SL} =\delta _S -2\delta _L $, carefully eliminating bound state contributions. In sequel, experimentalists have independently of $\delta _L $, measured $\delta _S $ with increasing precision and accuracy. A culmination of these efforts is the recent measurement of $\delta _S $ by Gabrielse et al. In view of the success recorded in the measurement of $\delta _S $, the question posed by Kusch et al will be reopened/discussed: Is it empirically justified to set $\delta _L $ equal to zero exactly? If we combine the recent measurement of $\delta _S $, together with that of $(\delta _S -2\delta _L )$, then it appears that$\delta _L =(-0.6\pm 0.3)\times 10^{-4}$. Does this imply that the electron orbital g-factor is also corrected?