Thank you for contacting Mearto and I apologize for the delay. Our site was recently revamped and for some reason your submission went into my ‘completed’ folder. Also, thank you for the extensive description. My appraisal is based on sales histories of similar pieces at auction along with a consideration of the material.
It’s important to note that amber is a particularly variably priced ‘stone.’ Prices generally follow these conventions:

Weight:
Weight is a problematic measurement insofar as the variation in types/quality of amber. (Something like determining the monetary value of a standardized mineral such as gold would be a straightforward calculation of weight.) For example, we have blue amber, amber with inclusions (biological material), and other rarities, as well as clarity, age and size per piece, all of which play a role in determination of value.

Weight per kg of semi-precious amber is between $5 and $15 per gram on average, so by this measurement, your 91 gram piece would be between $455 to $1365.

Size of pieces: the larger the individual piece, the more valuable.

Clarity: the clearer the amber, the more valuable.

With all this variation, it’s helpful to look at some recent hammer prices for amber necklaces that resemble yours. I arranged a representative list below by weight; all are very similar in style and color to your piece.

My Fair Market Value estimate is between $3000 and $4000, reflecting the price range I found for the majority of similar necklaces. However, you can see that there were notable outliers in prices.

Also, please see my notes at the bottom about authenticity and age.

$1750, EY (egg yolk), 30 g
https://www.liveauctioneers.com/item/45530812_antique-natural-butterscotch-egg-yolk-amber-necklace

$7000, 33 grams
https://www.liveauctioneers.com/item/74558065_an-amber-necklace

$250, 37 g, EY
https://www.liveauctioneers.com/item/102772913_no-reserve-price-eggyolk-amber-necklace-with-gold-clasp

$3000, 38 grams
https://www.liveauctioneers.com/item/52722353_butterscotch-amber-necklace

$950, 40 g, EY
https://www.liveauctioneers.com/item/44911462_egg-yolk-amber-necklace

$570, 40 g, EY
https://www.liveauctioneers.com/item/37470087_antique-natural-butterscotch-egg-yolk-baltic-amber-bead

$6000, 41 grams
https://www.liveauctioneers.com/item/98774935_an-amber-necklace

$300, 47 g, EY
https://www.liveauctioneers.com/item/53170271_vintage-natural-egg-yolk-baltic-amber-bead-necklace

$650, 60 grams
https://www.liveauctioneers.com/item/29541259_amber-necklace

$2040, 60 grams
https://www.liveauctioneers.com/item/44038460_amber-necklace-6

$850, 60 g, EY
https://www.liveauctioneers.com/item/102772917_no-reserve-price-eggyolk-amber-necklace

$150, 60 g, EY
https://www.liveauctioneers.com/item/83983388_baltic-amber-egg-yolk-color-28-graduated-bead-necklace

$1200, 74 grams
https://www.liveauctioneers.com/item/28386186_real-beautiful-baltic-amber-necklace

$2400, 74 grams
https://www.liveauctioneers.com/item/44038455_amber-necklace-2

$2680, EY, 85 g
https://www.liveauctioneers.com/item/71589809_100-natural-baltic-egg-yolk-amber-necklace

$5400, 94 g
https://www.liveauctioneers.com/item/25472142_a-butterscotch-amber-bead-necklace-the-graduated-amber

$3800, 97 g
https://www.liveauctioneers.com/item/44026813_a-natural-amber-bead-necklace-comprising-forty-three

$2150, EY, 126g
https://www.liveauctioneers.com/item/72625218_egg-yolk-amber-graduated-beaded-necklace

Notes on imitation amber vs. real:

Resin, copal, bakelite or plastic are sometimes used to imitate amber, so it is useful (and easy) to test authenticity. I like this site for a list of different ways to test amber:
https://bit.ly/2TFLumx

There are also ways to distinguish between precious (older and more expensive), copal (less developed amber) and semi-precious amber:
https://rock-candy-gems.com/pages/amber-gemstone-value-and-properties (see comparison lists midway down the page)

(I am assuming yours is semi-precious for the appraisal -- it’s most common.)