I`d never heard so many terms. In practice we used just two - opened and closed. (same as "without heel" and "with heel").
P.S. just to correct a little of writting - not ЛастА (female kind), in the old soviet books this term is ЛасТ (male kind)
- another models of Aquanavt by Red Rubberer from you
Soviet masks: Ukrainian models
I appreciate the grammatical correction, АлександрД. Thank you.
And you're right that the majority of diving manuals just make a distinction between open-heel and closed-heel fins.
The intermediate category of "semi-closed/semi-open heel" was used by two Soviet diving manual authors, I. V. Merenov and P. P. Serebrinitsky.
I. V. Merenov: "Весьма многочисленные образцы ласт по их устройству подразделяют на
открытые, не имеющие подошвы в пяточной части ступни,
полуоткрытые — с подошвой по всей ступне и
закрытые, которые надевают на ноги как туфли.
Водолазные боты, галоши и ласты для глубоководного погружения
Rough translation: "In terms of their design, many fins are divided into
open-heel models, which come without soles for the foot at the heel;
semi-open-heel models, which come with soles for the entire foot; and
closed-heel models, which are worn on the feet like shoes."
P. P. Serebrenitsky: "В зависимости от вида крепления и характера исполнения задника ласты можно подразделить на
открытые,
полузакрытые и
закрытые.
Открытые ласты имеют оформленную полость до половины ступни и удерживаются на ноге сплошным или регулируемым пяточным ремнем.
Полузакрытые ласты отличаются от открытых лишь наличием резиновой подошвы.
Закрытые ласты имеют полностью оформленный задник и надеваются как туфли, удерживаясь на ноге либо ремешком на подъеме либо (при глубокой туфле) за счет эластичности самой туфли.
Маски (полумаски, очки), дыхательные трубки, ласты
Rough translation: "Depending on the method of attachment and the nature of the heelpiece design, fins may be divided into
open-heel type,
semi-closed-heel type and
closed-heel type. Open-heel fins come with a cavity covering up to half the foot and they are held on the foot with a fixed or adjustable heel strap. What distinguishes
semi-closed-heel fins from
open-heel fins is just the presence of the rubber sole at the heel.
Closed-heel fins come with a complete heelpiece design and they are worn like shoes; they are held on the foot either with a strap at the instep or (if the shoe has a deep enough heel-cup) by the elasticity of the shoe itself."
Here's a drawing of the Mosrezina Model 2 fin, which may have been the first "semi-open/semi-closed" fin in the USSR:
I suppose that Merenov's and Serebrinitsky's argument goes as follows: Mosrezina Model 2, and others like it, is neither an open-heel fin because the sole is extended under the heel, nor a closed-heel fin because the back and sides of the heel are left uncovered except for the detachable adjustable heelstrap. It's a hybrid design.
