Need Help With Cover Paquebot Seepost Liberia-Southampton-Us

This is a cover which I got yesterday, sent from Liberia to USA.
it is stamped with Liberia stamps, with cancellation on stamps.
"DUTSCHE SEEPOST LINE, HAMBURG-WESTAFRICA" date not clear ending with 04 ie (1904).

It has another cancellation (seems to be transit cancellation)
"SOUTHAMPTON , (not clear SHIPS LETTER) dated 3PM 15JAN 04

Reverse side have two cancellations of "PHILADELPHIA " on 26 JAN 04 at 10.30AM AND 11.30 AM .
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Is this seepost same as Paquebot, are seepost mails posted at land or at ship.
I couldnt find it exactly my doubt is that whether the SEEPOST is similar to AIRMAIL , ie posted at postoffice and carried by sea.
Please have a look.
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I have very little experience with Paquebot or Sea Post mail and markings but find them fascinating.

The ones I have seen were posted on St Pierre et Miquelon islands and landed on the mainland at Nova Scotia, Canada and were stamped Sea Post there at Sydney Mines I think it was.

So, from those examples and I think others I have seen ( a while ago now) I am thinking that something marked Ships Letter was posted at sea or on board ship but something marked sea post is something received from a ship by a post office on land and forwarded on through their mail system from there.

Remember that at that time every stop at a post office along the way had to be recorded by stamping / cancelling the piece of mail.

Paquebot is something that could be either, depending on the country or colony at the time. A ship could stamp paquebot (I think beginning in 1892 or so) or the land based receiving postal office or depot, but most likely the ship, depending on the size of the ship or vessel also.

Different lines (ship companies) would have different markings but you always had to use the word paquebot or similar in English or perhaps the language of the country (not sure).

Some of the above is guess work by me, so just take it as an educated guess at what was going on at the time. Some I did know but may have forgotten some also.

Thankyou Puzzler for the comments.
But what confuse me from a mail posted at sea is that there is a postmark at the reverse of the envelope "DEUTSCHES KONSULAT MONROVIA" (it is posted to German consulate in Philadelphia )Which is an indication that it is posted from land.

I collect German colonies, and I've seen numerous instances where mail that didn't originate on the ship was cancelled on board. It seems that on occasion, if a local post office was unavailable for whatever reason, outgoing mail was delivered to the ship where it could be cancelled using the on-board canceller.

What's really curious to me is that the Hamburg-Westafrika Line cancel appears to be 1 March 1904.

You can try poking around here.

http://www.tpo-seapost.org.uk/

Thank you Postmaster and stallzer I have two more covers of same class which is actually the part of my collection.. ie the elephant covers.
Cover posted from Liberia sent to Germany through "DUTSCHE SEEPOST LINE, HAMBURG-WESTAFRICA"
Liberia Cancelled/ship cancelled: 11.06.1901
Altona Elbe Cancellation: 26-06-1901

This is as I understand it
Seepost/Sea Post markings are found on covers and cards posted at sea during the heyday of the Passenger Liners from about 1891 until around 1940.

The difference between the Seepost/Sea Post marking and the Paquebot marking is that Seepost/Sea Post was applied to letters posted at post offices located onboard the ships, and Paquebot markings were applied at shore post offices to mail received from ships that did not have onboard post offices.