Outside of a completed transaction, value has no meaning, so please do not ask me to value your guitar. Harmony instruments were produced on an industrial scale.
Even the less common models can't be considered "rare".
H1 H1141 H1203 H1213 H1214 H1215 H1260 H1265 H1266 H1310 H1311 H1325 H1327 H14 H1407 H1414 H1415 H1456 H1457 H15 H15V H162 H165 H16B H16R H16W H17 H173 H174 H19 H22 H22/1 H27 H37 H38 H39 H41 H42 H44 H45 H46 H47 H48 H49 H50 H51 H53 H53/1 H54 H54/1 H55 H56 H56/1 H57 H58 H59 H59/1 H60 H62 H63 H64 H65 H66 H68 H7 H70 H71 H72 H73 H74 H75 H76 H77 H78 H79 H802 H81 H82 H82G H88 H929 H945 H950 H954 H956 - If you're a buyer, the value is the max price you are ready to pay to have it.
If you're a seller, the value is the minimum amount you accept to sell it.. You can check ebay for completed sales for the same model, but value on ebay is not value in a shop or elsewhere, for reasons.
For example, on the photo below this guitar is without doubt a H22 (You can type a model number, with the H, on the search box on top of this page).