I have noticed in the Angelus Press ORDO that the Masses of the Invention of the Holy Cross (May 3), S John before the Latin Gate (May 6), and the Apparition of S Michael (May 8), may be said as IV class festal Masses because they are included by the 1962 Missal in its Appendix. I presume this information is accurate, and commend it to those whom it may concern. (Let's have no pedantry here: any pick-axe to break the pack-ice is to grabbed with both hands.)
This Appendix appears to have some parallelism with the provision by the 'Gregorian' Sacramentary of the texts which follow the Praefatiuncula Hucusque ( ... illa collegimus, in quibus, cui animo sedent, potest repperire)! Similarly, after S Pius X had shifted onto fixed days of the month all those festivals which earlier devotional habits had plonked onto fixed Sundays, ORDOs continued to offer some relief from this now-fashionable austerity: "Hodie celebrari potest unica Missa Sanctissimi Nominis Mariae", or even "Hodie celebrari possunt omnes Missae (praeter Conventualem) Sacratissimi Rosarii BMV" (check this out in your St Lawrence Press ORDO). It is a shame that the merciless, ruthless, singleminded revisers of the period Pius XII-Paul VI were so sure of themselves and had so little humanity, so little respect for the inculturated pieties and affections of ordinary clerics and laics. What an unprecedented rupure they did insist upon!
I do not possess a copy of the 1962 Missal; I would be genuinely grateful if readers who do have one could keep me posted about little matters of interest, such as this Appendix, which I might have missed.