Which PIE participle corresponds to PGmc past participle?

Question

Which PIE participle (active/middle/passive voice) corresponds to PGmc past participle?

Answer 1

The Proto-Germanic (and Latin, and others) past passive participles correspond with the Proto-Indo-European verbal adjectives:

From Beekes' 2011 p. 280:

18.9.2 The verbal adjective
This is an adjective that is not derived from a tense stem, as is the participle, but from a root. The most frequently found is the adjective in *-to- the root has zero grade.
 
    Skt. *syūtá-‚ ‘sewn’, OCS šitъ < *sjū-tъ, Lith. siṹ-tas
    Skt. *gatá-, Gr. *batós, Lat. (in)-ventus ‘arrived’ < *g^wm-tó-
    Lat. tentus ‘stretched’ < *tn-to-
    Arm. lu ‘known’ < *ḱlu-tó-
    Goth. nasiþs ‘saved’ < *-tó-s

Germanic uses this suffix to form the verbal adjective of weak verbs, as in E. fill-ed. [Emphasis mine.]

    The same function as *-to- was fulfilled by *-no-:
    Skt. bhinná- < *b^hid-nó- ‘split’
    Skt. pūrṇá- ‘full, filled’, OCS plъnъ, Lith. pìlnas, OIr. lán, Goth. fulls, all from *plh₁-no-, Lat. plēnus (with full grade)

The suffix form *-eno- is found in OCS vlьčenъ ‘pulled’. In Germanic *-ono- is used for the strong verbs: Goth. bit-ans < **-onos, E. bitten (sometimes *-ino-: Runic slaginaz,
OS geslegen ‘beaten’).

In PIE, these weren't participles proper, but verbal adjectives, even if many daughter languages they functioned like participles:

From Luraghi, Inglese, and Kölligan 2021:

Ancient IE languages attest to nominal forms of the verb, participles and verbal adjectives that may have a passive orientation when based on transitive verbs, that is, they may profile the event encoded by the base verb from the perspective of the Patient or P-participant. Notably, though the details of the morphological shape and the semantics of these morphemes differ in the IE languages, most of these forms, e.g. -nt- participles, *-to-, *-no-*, and *-lo- verbal adjectives, can be traced back to PIE (see Adrados et al. 2016: 369–375; Beekes 2011: 279–280; Fortson 2010: 108–109; Meier-Brügger 2010: 317–320, 421). **It must be stressed that in the system of the proto-language these were derivational deverbal morphemes, i.e. they were not obligatory and were not integrated in verbal inflectional paradigms, as is also shown by their partly idiosyncratic semantics. Accordingly, the -nt- and the -to- suffixes were used to derive verbal adjectives from verb bases and were originally indifferent to voice distinctions (Melchert 2017; Szemerényi 1996).