I am reading some county document from Qing Dynasty. Most of the prefaces were signed by 年號+（年）+干支紀年+（月）+籍貫+姓+名+（字）. For example, 康熙(年號)丙寅(干支紀年)會稽(籍貫)徐(姓)世法(名)序, 道光(年號)二十九年（年）歲次巳酉(干支紀年)十月上浣（月）皖江(籍貫)劉(姓)慶遠(名)序.
Yet there's a confusing use of 甫 and an familiar use of 氏.
One is signed by ...王謙言山介甫序. 王 is his family name, 謙言 is his name and 山介 is his 字. Then what does 甫 mean? Is it used as 男子的美稱? But it seems weird to use it for oneself or after a two-character 字. Or does it goes with 序? Yet I didn't find any dictionary entry or suitable google search results.
The other is signed by ...雲間陸箕永二水氏序. 雲間 is his 籍貫, 陸 is his family name, 陸箕 is his name and 二水 is his 字. After 姓 and 氏 had merged, the character 氏 is normally used after one's 姓, in this case 陸氏, but it does seem unofficial. Is there a convention to add 氏 after 姓+名+字, after 姓+名 or simply after 姓 for a single person
for official usages, not restricted to signing? If so, does 籍貫 has to be paired, as we often see 范陽盧氏、清河崔氏 etc? But these cases refer to a whole large extended family, not a single person.
PS: I've deleted "official context" from the original question since it doesn't seem to be what makes the difference.
I've read something from 《中国人的姓名文化与命名艺术》.
甫, 男子的美称, originally 父. It's essentially connected with one's 字. In some classics, we can see 甫xx, that is that person has 字 of xx.
甫 and 父 can be used interchangeably. For example, 王安石 and his brothers had 字 x甫, and he called them x甫 or x父.
甫 is used as a 衬字 in 字. In Zhou Dynasty, the template of 字 is 排行+单字+甫, e.g. Confucius is 仲尼父. The short-hand is 尼父. After turning 50, he could also be called 仲尼.
This tradition is abandoned after Zhou and 字 became predominantly 2 characters. 衬字 could also be used. Some incorporate 排行, some keep 甫. For example, 曹操，字孟(排行)德；王安石，字介甫.
Some paper says that the legacy of 甫 after a 2-character 字 is kept but doesn't give evidence. I find it questionable. 3-character 字 are very rarely used after Han Dynasty, and the cases I see are all transliterations and used by non-Han ethnics.
However, there is indeed a famous example from 《核舟记》, 虞山王毅叔远甫刻. 王毅, 字叔远. But this case is a bit coincidental, since 叔(排行)远甫 happens to follow the Zhou tradition and does not necessarily mean the 字 山介 can be traditionally used the same way. There's a paper which explains 甫 as 才 just, saying it was just engraved. The argument is that 字 cannot be used to address oneself. I find it hard to believe. On the one hand, there are cases where 字 is indeed used by famous literati to call oneself （古人能否称自己的字？ - 不诉离殇的回答 - 知乎 https://www.zhihu.com/question/37522182/answer/2542179133 ）. On the other hand, give 甫's close connection with 字, even if the author wanted to write just, he was likely to choose another word to avoid confusion.
So far my question of 甫 is partly resolved. The unresolved part can be specified to, is there a legacy to use 甫 after one's 字 (almost all 2-character)? If so, under what conditions can it be used?
氏, is a synonym to 族, which was essentially the name of the tribe, and the later the name of the tribal alliance. In Zhou Dynasty, country/nation was established, and 国号 replaces 氏. People then recycled 氏 and used it to refer to branches of 姓. After Warring States, 姓 and 氏 merged. People 以氏为姓 and 姓氏 has since become an integral part of one's full name. So using the character 氏 after one's 姓 is easy to understand. 陆氏 is literally 以陆为姓氏（的人/家族）, refers either to a single person or a clan. For example, 他是范阳卢氏, referring to a single person, 他是范阳卢氏之子, referring to the clan.
In this case 籍贯 should be used together. Counterexample from 《史记》今蒙氏，秦之大臣谋士也. For women, their names are not important in feudal dynasties, often called 姓+“氏”, e.g. 卢氏, 籍贯 is often not added if not famous.
After knowing this, it makes the usage of 陸箕永二水氏(姓+名+字+“氏”) even weirder to me.