Wikipedia: In Buddhism, the three marks of existence are three characteristics (Pali: tilakkhaṇa; Sanskrit: trilakṣaṇa) of all existence and beings, namely impermanence (anicca), unsatisfactoriness or suffering (dukkha), and non-self (anattā).
As far as I know, in modern China, many translators confused tilakkhaṇa（三相） with tri-dṛṣṭi-namitta-mudrā（three dharma seals，三法印）.
The concept of “3 dharma seals” is very famous in the Northern Buddhism, which came from Nāgārjuna’s Mahāprajnāpāramitāśāstra（Great Treatise on the Perfection of Wisdom，大智度论）. But it originated in the Saṃyuktāgama.
SN.22.90/(8).Channasuttaṃ
All formations are impermanent; all phenomena are nonself.
Sabbe saṅkhārā aniccā; sabbe dhammā anattā”ti.
But in the paralleled SA 262, there is one more phrase:
一切行無常，一切法無我，涅槃寂滅。
(All formations are impermanent; all phenomena are nonself; the nirvana is silent.)
I figure that this was the sutta from which Nāgārjuna cited and made the concept of 3 dharma seals.
The three marks (tilakkhaṇa) are:
- sabbe saṅkhārā aniccā
— “all saṅkhāras (conditioned things) are impermanent” - sabbe saṅkhārā dukkhā
— “all saṅkhāras are unsatisfactory” - sabbe dhammā anattā
— “all dharmas (conditioned or unconditioned things) are not self”
The three dharma seals (tri-dṛṣṭi-namitta-mudrā) are:
- anityāḥ sarva-saṃskārāḥ
—all saṃskārāḥ (conditioned things) are impermanent，诸行无常 - nirātmānaḥ sarva-dharmāḥ
—all dharmas (conditioned or unconditioned things) are not self，诸法无我 - śāntaṃ nirvāṇam
——nirvāṇa is silent，涅槃寂静
They are different, but also a little similar.