*This is a working item, but the operating time has not been measured.
■ Condition of scratches and dirt
Crystal: Minor
Case back: Minor
Bezel: Minor
Strap: New aftermarket part
Calendar: Day quick-set possible, Day of the week quick-set not possible

Meaning of Seikomatic Series and "R"
First, the Seikomatic series is one of Seiko's automatic dress watch lines developed in the 1960s.

This Seikomatic series has variations such as slim models (Slim / Slim-Date, etc.), models with date functions, and even "Seikomatic-R" (where "R" is understood to mean "Robust" or "Revised," or is a differentiating name).

Multiple examples of Seikomatic-R models using the 8300 series (especially 830 / 840 → 8305 series) movements have been confirmed.

For example, reference 8305-1010 is known as a representative example of Seikomatic-R, and an individual believed to be manufactured in 1966 with an 8305 series movement has been confirmed.

Lineage of 8300 Series Movements (especially 830, 840, 8305, 8306, etc.)
The 8300 series movements (830, 840, 8305, 8306, etc.) used in Seikomatic-R are considered to have a slightly different design philosophy from other Seiko automatic movements.

The "830" as a base movement was designed as a slim automatic movement without a date function, and it is believed to have been developed into the 840 series, which later incorporated a date function.

The 840/8305 series features the addition of a date mechanism and, in some variants, a manual winding mechanism.

The 8306 series is sometimes introduced as "83 Matic Week Data" and is considered a parallel or expanded movement to the 8305 series.

Models with a movement number including "8306" are likely to have a date function or be an improved version, but there is not much information found in sources regarding specific models or specifications equipped with the 8306.

Furthermore, the Seikomatic series as a whole is described as having a production period roughly from the early 1960s to around 1967.

Estimates and Precautions Regarding Reference 8306-8001

Regarding the model number 8306-8001 that you mentioned, the following points can be considered:

"8306" likely refers to the model series equipped with the 8300 series movement mentioned above.

The "8001" part is likely the case/module number indicating the case shape, dial specifications, lug shape, dial design, etc. (Many Seiko models have reference numbers in the format "Movement Number - Case Number").

However, in lists of Seikomatic/Seikomatic-R models in literature and online, specific specifications or actual examples (with photos and operational checks) of the 8306-8001 have not been confirmed to date (at least not appearing in major Japanese or English sources).

Therefore, the 8306-8001 may have had relatively minor specifications (or specifications for limited regions or domestic distribution).

If you have specific information about the actual 8306-8001 (engravings, movement caliber, dial markings, etc.), it may be possible to estimate more details based on that.