  Two mechanisms are examined for hard double pomeron exchange dijet
production, the factorized model of Ingelman-Schlein and the nonfactorized
model of lossless jet production which exhibits the Collins-Frankfurt-Strikman
mechanism. Comparison between these two mechanisms are made of the total cross
section, $E_T$-spectra, and mean rapidity spectra. For both mechanisms, several
specific models are examined with the cuts of CDF, D\O and representative cuts
of LHC. Distinct qualitative differences are predicted by the two mechanisms
for the CDF $y_+$-spectra and for the $E_T$-spectra for all three experimental
cuts. The preliminary CDF and D\O experimental data for this process are
interpreted in terms of these two mechanisms. The $y_+$-spectra of the CDF data
is suggestive of domination by the factorized Ingelman-Schlein mechanism,
whereas the D\O data shows no greater preference for either mechanism. An
inconsistency is found amongst all the theoretical models in attempting to
explain the ratio of the cross sections given by the data from these two
experiments.
