These Thessalian horsemen are also very old models... some are RAFM and some are Ral Partha... these were the most detailed 25mm figures readily available in the USA for many years. Naismith models are better detialed in many respects, but I never collected many of those because they were difficult to come by. (in other words I needed both money, and mail order skills... nowadays the internet brings everything closer and easier no matter where on the globe it is shipped from).
The Thessalians were part of Alexander's army of conquest as he inhereited their allegiance when Philip was assasinated. They were renowned horsemen in Greece and their hit and run, tactics coined the phrase "Thessalian tactics." In earlier wars the Thessalians engaged as skirmish cavalry but by Alexander's time large numbers formed as heavy shock cavalry. The Thessalians covered the left flank of the Phalanx in the major battles agaisnt Persia. At Issos they suffered heavy losses when at least one squadron was overrun by Persian cavalry. Armament is conjectural, a grave stele from Thessaly shows an armored horsemen (who may be a Macedonian as his cloak is not a typical Thessalian style). It is possible that Thessalians armed themselves with lighter spears than the Companion cavalry, and may at times have used javilens, or even combined them.
Alexander's left wing was entrusted to Parmenion. This old Minifigs officer rides a white Ral Partha horse and has often sucessfully guarded the phalanx from being flanked.
"After the battle of Issus, he sent to Damascus to seize upon the money and baggage, the wives and children, of the Persians, of which spoil the Thessalian horsemen had the greatest share; for he had taken particular notice of their gallantry in the fight, and sent them thither on purpose to make their reward suitable to their courage."
translated by John Dryden